I've been a typography buff for years--I even reflexively groan when I see ads that use Helvetica--so this Flip Web site was just too entertaining for me to pass up.
It relies on a property of the Unicode character-encoding scheme, which has a vast array of letters and glyphs from non-Roman alphabets. Think of it as ASCII on steroids.
Unicode has enough characters that many standard Roman alphabet characters have upside-down equivalents. When you type letters into the upper box, they appear upside down in the lower box via Unicode translation, according to the site's designer, David Faden. … Read more