Workers' Edge

Internet Explorer 8, Firefox 3, Google Chrome 4, Apple's Safari 4, and Opera 10 include features that block sites known to host malware and malicious downloads. All but Opera also let you browse without leaving any tracks. But just as important as these protections is ensuring that whichever browser you use is thoroughly patched.

Filtering out bad sites
Firefox's built-in antiphishing tool claims to update its bad-site database 48 times a day, according to Mozilla's Firefox security page. Firefox 3 uses Google's Safe Browsing service to automatically block sites that are known to host malware. The Google Code site describes how Safe Browsing works in Firefox.

To verify that attack-site blocking is enabled in Firefox, click Tools > Options > Security and make sure "Block reported attack sites" is checked.

Firefox will prevent known-bad sites from opening when "Block reported attack sites" is checked.

(Credit: Mozilla Foundation)

The same feature is built into Google's own Chrome browser. You can ensure that malware-site filtering is on in Chrome by clicking the wrench icon in the top-right corner, choosing Options, and selecting Under the Hood. "Enable phishing and malware filtering" should be checked. The Google Chrome Help site describes the feature. (Hint: This page looks very similar to the description on the Google Code site.)

Google's Chrome browser blocks known-bad sites when "Enable phishing and malware protection" is checked.

(Credit: Google)

The SmartScreen technology in version 8 of Internet Explorer blocks known-malicious downloads as well as bad URLs. Other new security features in IE 8 include automatic blocking of click-jacking and cross-site scripting attacks, automatic crash recovery, and highlighting of the actual domain name in the address bar. The Microsoft Security site describes the SmartScreen Filter and includes links to a SmartScreen FAQ and information for site managers.

Apple's Safari browser added phishing and malware blocking in version 3.2, which was released in late 2008; read about this and other security features in Safari 4 on the Apple Safari site. Likewise, Opera's Fraud Protection predates the phishing and malware filters in IE and Firefox and is enhanced in the latest version 10. But attack-site blocking is only one of Opera's many security features, which you can read about on the Opera site.

Browsing in private
To activate private browsing in Firefox 3, click Tools > Start Private Browsing, or simply press Ctrl-Shift-P. You can set Firefox to start in private-browsing mode by clicking Tools > Options > Privacy and check "Automatically start Firefox in a private browsing session." The Mozilla support site provides more information about this feature. Likewise, put IE 8 in private-browsing mode by clicking Safety > InPrivate Browsing, or by pressing Ctrl-Shift-P. You can also open a new tab and click either Browse with InPrivate or Open an InPrivate Window.

IE 8 also lets you control the information about your browsing habits that's shared with Web tracking services. To activate this feature, click Tools > InPrivate Filtering Settings and choose "Let me choose which providers receive my information." This opens the InPrivate Filtering settings dialog, where you can turn filtering off, choose which services to block from tracking you, or automatically block all trackers.

Internet Explorer 8's InPrivate Filtering lets you block some or all Web tracking services.

(Credit: Microsoft)

You can open an incognito window in Google Chrome by clicking the wrench icon in the top-right corner and choosing "New incognito window," or simply press Ctrl-Shift-N. The incognito icon (a shadow figure in a fedora and glasses) appears in the top-left corner of the browser window. The Chrome support site offers a more detailed description of this feature.

Opera lacks an equivalent private-browsing capability but does offer private searching and other identity-blocking features, as described on the Opera site. To activate private browsing in Safari, simply click Safari Settings Menu > Private Browsing.

Automatic and not-so-automatic browser updates
Patching is a way of life with nearly all software, but especially with browsers and the media players associated with them: Adobe Reader, the Flash Player, Apple's QuickTime, and Sun's Java, among others. All of a browser's security features can be rendered useless by a piece of malware that takes advantage of an unpatched hole in the program.

Firefox 3 alerts users to the presence of an update and now also notifies you when your Flash Player is out-of-date. Internet Explorer 8 updates via the Windows Update/Microsoft Update services. Google Chrome made a splash by being the first browser to update itself in the background without requiring any prompting from users. Safari updates automatically via Apple's update service, which also serves up patches automatically for QuickTime, iTunes, and other Apple software. Opera also notifies you automatically when a new version is available.

But updating is too important to leave to others. Back in April, I described Secunia's Online Software Inspector and downloadable Personal Software Inspector, which identify out-of-date programs on your PC. The programs mentioned in that post have all been updated since, but Secunia's services should point you to the most recent versions.

(Note that Secunia sometimes reports a program as being out-of-date when in fact you have the latest version. On my PC, it continually reports my up-to-date Flash Player as being in need of an update, for example. But the free service Secunia provides is worth putting up with this and similar minor annoyances.)

There's no way to reduce to zero your risk of picking up some piece of malware while browsing. You need layers of security to keep viruses, Trojans, and botnets at bay—the more layers, the safer your browsing. (Of course, the more layers, the slower your browsing, too, so don't get carried away.)

Much emphasis has been placed on the enhanced security features of the latest versions of the popular browsers. Whether one is any safer than another is anybody's guess, but no browser gives you more ways to thwart a Web-based attack than Firefox via its wealth of security add-ons.

Link checkers add warnings to search results
Search results are often difficult to trust, even when the URL looks familiar. Phishers are adept at planting dangerous links that look like harmless ones. Link checkers provide you with an indication of the trustworthiness of sites before you click their links. (Note that several of the products are available for Internet Explorer as well.)

Some of the programs, such as McAfee's SiteAdvisor, give the thumbs-up or thumbs-down based on a single company's research. Web of Trust (WOT) bases its recommendations on the collective intelligence of a network of volunteers. LinkExtend is a link-check aggregator that combines the analyses of eight different services.

McAfee SiteAdvisor adds a safety indicator to Web search results.

(Credit: McAfee)

While the recommendations of link checkers are helpful in identifying safe sites, you can't take their yeas and nays as gospel. For example, sites that offer downloads of system utilities may be flagged as dangerous because the programs require access to the operating system and thus could do major damage in the wrong hands.

Track the trackers
You know popular Web sites download software that tracks your activities on their sites, but do you know who's doing the tracking? Find out with the Ghostery add-on that pops up the names of the trackers as the page opens. The program puts a small "ghost" icon in the bottom-right corner of the Firefox window that turns orange when trackers are present. Click the link that appears to the right of the icon to find out more about the trackers and block them individually or entirely.

The Ghostery Firefox add-on lets you know who's tracking your activities on the site.

(Credit: Ghostery)

View encryption specs
When you open an encrypted Web page, a lock icon appears in the bottom-right corner of the Firefox window and the URL in the address bar begins with "https." But there's more than one form of encryption, and knowing which type and strength of encryption in use can be handy.

The CipherFox add-on puts in the bottom-right of the Firefox status bar the Secure Sockets Layer/Transport Layer Security (SSL/TLS) cipher and keysize currently in use. Double-clicking the entry opens the CipherFox dialog box, where you can disable RC4 encryption and display partial SSL/TLS. (Note that the developer accepts donations to support the product.)

Take charge of Web password management
Firefox's built-in password manager lets you create a master password and remember passwords for specific sites, but if you want to get serious about managing your passwords, get LastPass, a password manager that provides much more granular control over your sign-ins.

After you download and install the add-on, an icon is placed in the top-right corner of the Firefox window. Click it to open the LastPass menu, which lets you manage your identities, open the LastPass Vault, jump to favorite sites, and generate secure passwords. You can also import or export sign-in IDs, compose and print secure notes, and assign keyboard shortcuts for specific actions.

In addition to Firefox and IE, LastPass is available for Google Chrome and Apple's Safari browsers. LastPass backs up your passwords by storing an encrypted copy on its own servers. And because you can access your passwords via the Internet, you can use LastPass on any Web-connected device, although use of LastPass on an iPhone or other smart phone requires a Premium membership, which costs $1 a month. (You can also put LastPass on a USB thumbdrive for use with Firefox Portable and other portable apps.)

Microsoft has made great strides in educating Windows users about the need to keep their systems secure by downloading and installing the most recent updates. (I still recommend that you set Windows' Automatic Updates to download but don't install, as I described in a blog post from last July.)

The irony of the heightened awareness of Windows updates is that malware is less likely to target vulnerabilities in Windows--or other PC operating systems, for that matter. These days, most viruses and Trojans use holes in your browsers, media players, or Web applications to breach your system's security. That's why it's imperative to keep these programs up-to-date, which is a subject I covered in a post from last April.

Google pushes updates to its Chrome browser automatically--without bothering to let you know about it (the current version is 2.0.172.30). You may think I'm a hypocrite for preventing Microsoft from loading its updates automatically and applauding Google for doing the same thing with its browser. Here's the difference: if a Chrome update causes the program to malfunction, I can simply use another browser, but if a Windows update screws up, my entire system's hosed until I fix it.

If you want to use Chrome to browse without leaving any tracks on your system, press Ctrl-Shift-N to open a new browser window in Chrome's incognito mode. The sites you visit subsequently will not appear in your browser history nor will terms you search for stay in your search history. You won't pick up any new cookies, either.

You'll find plenty of add-ons in the Privacy & Security section of the Firefox Add-ons page that give Firefox a similar stealth mode. You can also choose Tools > Clear Private Data to wipe your tracks in Firefox, but this setting erases all your history in the various categories. Chrome's incognito mode lets you retain the history you want and delete the history you don't want.

Google's Chrome browser lets you surf without leaving tracks on your system via its incognito mode.

(Credit: Google)

I've been spending a lot more time browsing with Chrome lately, and not just because of its incognito mode. Chrome seems faster to me than Firefox or Internet Explorer, and I'm getting used to Chrome's streamlined interface. Firefox remains my default browser, however. The one Firefox security add-on I won't browse without is InformAction's NoScript (donationware), which lets you block JavaScript, Flash, and other scripts on a site-by-site and source-by-source basis.

The best way to enhance your privacy while using Firefox is to set the browser to delete cookies each time you close the program. To do so, click Tools > Options > Privacy, select "Always clear my private data when I close Firefox," and click OK.

Check "Always clear my private data when I close Firefox" in the browser's Privacy settings to maintain your Web privacy.

(Credit: Mozilla Foundation)

So what about Internet Explorer? IE 8 is said to be more secure than IE 7, which in turn was said to be more secure than IE 6. Two facts remain: Internet Explorer uses ActiveX, which in my opinion is inherently insecure; and IE 8's security options are way too complicated. What do those slider controls mean, really? (Press Alt, click Tools > Internet Options, and choose either the Security or Privacy tab to see what I mean.)

Bonus tip: Encrypt Gmail
I've been using Gmail as my primary e-mail service for several years, but it wasn't until a couple of months ago that I started encrypting my Gmail correspondences. (In fact, encryption wasn't available in Gmail until a couple of months ago.) To use encryption in Gmail, click Settings in the top-right corner of the main window, scroll to the bottom of the General tab, select "Always use https," and click Save Changes. Note that this setting prevents the iGoogle Gmail widget from working, but that's a small price to pay for the added security.

Web privacy resources
For more information on the privacy options in Google services, visit the Google Privacy Center. Along with an FAQ and overview, you'll find privacy videos and specific privacy options for YouTube, Orkut, Blogger, Docs, and other Google services.

The SANS Institute's Internet Storm Center offers a daily Internet threat level (green, the last time I checked) as well as information on the sources of recent Internet-based attacks and extensive links to other Internet security sources.

For a soup-to-nuts look at browser security, read the United States Computer Emergency Response Team's article Securing Your Web Browser. The information was last updated more than a year ago but remains relevant. Some of US-CERT's browser-setting recommendations are overkill for regular, everyday browsing, so take the advice with the proverbial grain of salt.

I'll save us both some time by getting right to the descriptions of three Firefox add-ons that shave minutes off my workday. Hey, they add up!

Navigate Web pages using only your keyboard.
When it comes to speed, I'll take a keyboard over a mouse any day of the week. A post from April 2008 explains how to create a keyboard-shortcut list you can access quickly. I also wrote about using your keyboard to move and resize windows and shortcuts for Word and Excel.

Now I can park the mouse when I surf. Instead of clicking, I enter the number Rudolf Noe's Mouseless Browsing add-on places next to each link. If I want to put the cursor in the address bar, I enter 0, while pressing 00 puts the cursor in the search field. Each open tab gets a number, each text box on the page gets a number, each drop-down menu gets a number. (I just wish the bookmark toolbar options and the reload, stop, and home buttons did.)

The Mouseless Browsing Firefox add-on assigns a number to each link and option on a Web page so you get there from the keyboard.

(Credit: Rudolf Noe)

The program is loaded with options, including the ability to use only the numeric keypad to enter the numbers, so the top-row number keys aren't used to enter shortcuts. You can also require pressing the Enter key before the action occurs or change the delay between entering the numbers and taking the action.

Granted, the numbers can play havoc with a page's layout, but I can't count the number of times I've struggled to get the mouse pointer over just the right tiny link in a sea of tiny links. Being able to enter a number instead of clicking is a joy for this keyboard aficionado. (Warning: the add-on also slows your page-load speeds a bit.)

Finally! Copy Web text without the formatting.
I know how to create a keyboard shortcut that pastes plain text, but I didn't have the ability to copy and paste text from Web pages without the formatting until I downloaded Jeremy Gillick's aptly named Copy Plain Text add-on for Firefox. Just download the extension, restart Firefox, and when you copy text from a page, you'll see a Copy as Plain Text option just under the Edit menu's regular Copy option.

Copy Plain Text lets you do just that from Web pages in Firefox.

(Credit: Jeremy Gillick)

You also get the Ctrl-Shift-C keyboard shortcut to copy the text without formatting. You can say what you want about one-trick ponies, but I only wish all software was this straightforward. Of course, Firefox could have this feature built in, but I'm not complaining.

The latest scores are a right-click away.
OK, I admit it. If I'm working late and missing a big game, I visit a sports site to check the scores. Now I save myself time by right-clicking Vinny 2020's SportsFox add-on, choose the sport, and see that yes, the Tigers dropped another one to the Bosox, and even worse, the Red Wings lost their second game of the Stanley Cup finals the the Penguins. (Might as well keep on working.)

Get up-to-the-minute sports scores inside your browser with the SportsFox add-on.

(Credit: Vinny 2020)

Now I'm going to enjoy some of the time these add-ons have saved me. Go Wings!

The first program I open every day is Firefox, and most days the first Web site I visit is Google. That's why I'm glad so many Firefox add-on developers have created tools that give me a new perspective on my Google search results. Here are three of my favorites.

Sharpen your searches with GoogleEnhancer
The primary reason I click Google's Advanced Search option is to limit the results to a specific date range. With NettiCat's GoogleEnhancer add-on I can narrow my searches by date as well as by file type and a handful of languages via drop-down menus that are placed to the right of the search box.

The GoogleEnhancer add-on for Firefox puts drop-down menus next to the text box that let you narrow your results by time, language, and file type.

(Credit: NettiCat)

As nice as the search enhancements are, one of my favorite GoogleEnhancer features is the addition of icons to the left of the results for each link's site. The add-on also numbers the results, though these don't really add much to the results, in my opinion.

... Read more

Sometimes, it pays to go with your first instinct.

For the last couple of weeks, every time I opened the Firefox browser on my PC, the program attempted to update but failed. I didn't sweat the error message at first, thinking that it was likely a widespread problem that the good folks at Mozilla would address soon enough. And besides, version 3.0.4 opened right after I closed the error message, and everything appeared to be working normally.

I kept, however, getting that same error message every time Firefox loaded. It struck me that one of the things viruses do is block your security and other programs from updating. I didn't think that this failure was a sign of a virus, but I couldn't be sure.

Opening Firefox 3.0.4 generated this cryptic error message after failing to update to version 3.0.5.

(Credit: Mozilla Foundation)

My first inclination was to uninstall version 3.0.4 and then install Firefox 3.0.5 manually. But on second thought, this struck me as too extreme. After searching the Internet for information about failed Firefox updates, I chased many a wild goose as I disconnected my Webcam, rechecked my firewall, and followed many other useless pieces of advice recommended by reputable Web sites.

All to no avail. So I opened Vista's Programs and Features (the equivalent of XP's Add or Remove Programs applet) by pressing the Windows key, typing appwiz.cpl, and pressing Enter. I uninstalled Firefox 3.0.4, closed the applet, and opened the Opera browser so I could visit Mozilla.org to download Firefox 3.0.5.

This is where things took a slight detour. I don't use Opera very often, so it wasn't a surprise to see a prompt to download the latest version 9.63. I'm sure that Opera 9.62 would have downloaded the Firefox 3.0.5 executable just fine, but I figured that I might as well keep the update thing rolling.

But then Opera wouldn't update. The error message said something about my G: drive. I opened Windows Explorer and saw that I had no G: drive. Then I remembered that I set Opera to run off a USB thumb drive, which I had recently disconnected. I retrieved that drive and tried the Opera update again. This time, version 9.63 installed without a hitch.

And wouldn't you know it, so did Firefox 3.0.5, once I downloaded it from the Mozilla Foundation site. I suppose that I should be curious about why the browser wasn't able to update itself in the first place, but I'm satisfied just to have the latest version in place.

A big reason for the growing popularity of the Mozilla Foundation's Firefox browser is the amazingly creative and abundantly useful add-ons that are being created for Firefox. My three new favorites let you ax the ads on a site, see the tracking pixels on the current page, and gain a wealth of options when you select and right-click text in your browser.

Browse faster by blocking ads
Wouldn't you like to watch TV and listen to the radio without having to sit through the ads that pay the freight? Or dismantle the billboards that line the freeways? I can't help you with TV spots or roadside distractions, but you can kiss Web ads good-bye. Just download and install Wladimir Palant's Adblock Plus extension for Firefox.

After browsing with Adblock Plus enabled for a while, I started to wonder how I ever managed to surf without it. I noticed an immediate increase in the load speed of many of the sites I visit frequently, such as ESPN.com and CNN.com. And it's so much easier to find the information I'm looking for on a crowded page without all the ads getting in the way.

When you restart Firefox after installing Adblock Plus, you're given the option to import a set of filter rules or create your own rules. I took the easy route and opted for the canned filters, which do a good job of removing the ads from the sites I frequent.

You can view the number of blocked items on the current page by hovering the mouse pointer over the "ABP" icon in the top-right corner of the Firefox window. Or click the down arrow to the right to access the extension's preferences and other options.

View the number of blocked ads on a page by hovering over the ABP icon.

(Credit: Wladimir Palant)

Some ads manage to slip past Adblock's filters, but you block them in the future by right-clicking the ad and choosing Adblock Image. There are a wealth of other options in the program; visit the developer's FAQ page for more information.

Know when you're being tracked
I'm usually not very curious about which of the Web-tracking services may have planted a pixel in the Web pages I visit, but knowing which sites use which tracking services gives me a little more information about what I can expect from the people behind the site.

Jan Bogutzki's Counterpixel detects the presence of tracking pixels from 19 different services, including Google Analytics, WebTrends, and Site Meter.

Counterpixel doesn't block the trackers; it merely alerts you to their presence on the current page. This might provide more information than the average Firefox user needs, but the add-on is a great way to find out a little bit more about the sites you frequent.

Get more right-click options for selected text
I've been using the Hyperwords extension for only a few days, which is not nearly enough time to learn all the text tricks this program performs. The first Hyperwords feature that caught my eye was the Translation option, which lets you convert the selected text into more than a dozen languages.

Customize the right-click options that the Hyperwords extension adds to Firefox.

(Credit: Hyperwords)

Other Hyperwords context-menu options let you search for the selected text at various reference sites and view other occurrences of the text on the page by sentence or paragraph, among other alternatives. You can also save the selection as a text file or send it directly to your printer.

It's a mystery to my why more people still use Internet Explorer than Firefox or any other competing browser. But I don't get the success of American Idol, either, so it must be me.

The second of my three-part update of the 10-Step Security story I wrote three years ago shows that some tech advice stands the test of time. (A post earlier this week freshened up tips one, two, and three from that story, which focus on Windows updates and security features.)

Step 4: Ensure that you can see file extensions and all Windows system files in Windows Explorer and folder windows.

These days, you're less likely to encounter a dangerous executable file masquerading as a harmless type of file, but viewing file extensions and hidden files remains a good idea. The steps in the original article for making this change in XP are the same in Vista's version of Windows Explorer, though you may have to press the Alt key to show the Tools menu.

Step 5: Set the security level of Internet Explorer's Internet zone to High.

There's nothing stale about this advice. Of course, you should now be using IE 7 rather than IE 6, which is much less secure than its successor. The steps to reset your Internet zone security level are a bit different in IE 7: click Tools > Internet Options > Security, choose Internet in the box of zones at the top of the dialog box, move the security-level slider to High, and click Apply or OK.

Set Internet Explorer 7's Internet zone security level to High.

(Credit: Microsoft)

As the original article stated, this security level will generate pop-ups whenever you try to open a site that's not on your approved list. To add sites to this list in IE 7, choose the "Trusted sites" icon in the zone box at the top of the Security dialog box, click the Sites button, type the site URLs in the top box one at a time, and click Add. Keep the option on the bottom to require server verification unchecked.

Add the sites you trust to Internet Explorer 7's whitelist.

(Credit: Microsoft)

Step 6: Use the NoScript add-on to block scripts in Firefox on a page-by-page and element-by-element basis.

Of course, the simplest way to improve your chances of staying safe on the Web is to use a browser other than IE. I'm not saying Firefox, Opera, and other browsers don't have flaws of their own. It's just that those programs aren't targeted by the bad guys as often as IE is.

Giorgio Maone's NoScript add-on for Firefox lets you decide which scripts are allowed to run before the page loads. NoScript was relatively new back in 2005 when that article was written, but the program has stood the test of time. Note that the program's author accepts donations to offset the cost of maintaining and updating the application.

Another option for blocking Flash content in Firefox is by using Nicolas Martin's Flash Killer add-on. Apart from ensuring that no malware finds its way onto your PC via a Flash file embedded on a Web page, the program speeds up your browsing by blocking Flash ads from loading along with the regular content of the page.

In my next post, I'll revisit the last four tips in 10-Step Security, which deal with e-mail safety.

I have banished the Yahoo Toolbar from my PCs. It's not that I have anything against Yahoo. I use many of the company's services.

It's just that for me, the shortcuts on the Yahoo Toolbar don't justify the lost screen space, especially on my 13.3-inch laptop display.

So imagine my surprise when I happened to find the Yahoo Toolbar listed among Firefox's add-ons. (It snuck in when another user of the machine downloaded the Yahoo IM client.)

You might be surprised by the add-ons and extensions that have wormed their way into your copy of Internet Explorer 7 or Firefox 3.

You can work your way through the list of add-ons in your favorite browser, disabling and uninstalling those you don't need. Or you can save time by opening IE 7 and Firefox 3 with all add-ons and extensions disabled.

To open Internet Explorer with no add-ons or ActiveX controls working, click Start > All Programs > Accessories > System Tools > Internet Explorer (No-Add-ons). (In Vista, a faster way to open IE with no add-ons is by pressing the Windows key, typing Internet Explorer, and choosing Internet Explorer (No Add-ons) in the resulting list of shortcuts.)

To disable all of Firefox's add-ons, you have to open the browser in its Safe Mode (no relation to Windows' own Safe Mode) by clicking Start > All Programs > Mozilla Firefox > Mozilla Firefox (Safe Mode). A quicker way is to press the Windows key (in XP, follow this by pressing R), type Firefox -safe-mode, and press Enter.

Disable all add-ons in Firefox by starting the browser in Safe Mode and selecting the "Disable" option.

(Credit: Mozilla)

In the Firefox Safe Mode dialog box that appears before Firefox opens, click "Disable all add-ons" and choose the Make Changes and Restart button to run the browser with no add-ons or extensions enabled.

I can't tell you for sure that every feature of every Web site you visit will work as designed, nor can I say unequivocally that you'll be browsing faster with no add-ons enabled. But I made the rounds of my favorite sites in each browser's no-add-ons mode and didn't feel like I was missing anything. In fact, the only way I knew my add-ons were disabled in IE was seeing the Manage Add-ons option grayed out on the Tools menu.

The "Manage Add-ons" option on IE's Tools menu is grayed out when you open the browser with all add-ons disabled.

(Credit: Microsoft)

Disabling add-ons and extensions one at a time is a snap in both Firefox and IE. In the former, click Tools > Add-ons, select an entry under the Extensions tab, and click Disable. To toss an extension, click Uninstall. You can disable (but not uninstall) Firefox's plug-ins by clicking the Plug-ins tab, selecting an entry, and clicking Disable.

In IE, you can turn off add-ons one by one by clicking Tools > Manage Add-ons > Enable or Disable Add-ons. You have your choice of four views on the Show menu at the top of the Manage Add-ons dialog box (the default is "Add-ons currently loaded in Internet Explorer"). To disable an add-on, select it and choose Disable at the bottom of the dialog box.

You have a choice of four views when enabling or disabling add-ons in IE's Manage Add-ons dialog box.

(Credit: Microsoft)

One reason you may need to disable your browser's add-ons is to troubleshoot poor performance. Microsoft provides a step-by-step guide for fixing problems with Internet Explorer, and one of the steps is disabling your add-ons and re-enabling them individually until the problem recurs, at which time you've found the troublemaker.

You'll find more information about Firefox add-ons at the Firefox Support Knowledge Base.