There is a great rant on Bird on a Wire about Web designers' ignorant use of Helvetica in their pages. Bottom line: Helvetica was not designed to be read on a computer screen. Designers at Apple long ago decided to name screen fonts after cities. If you want to specify a screen font on the Mac, your choices include Chicago, Geneva, Monaco, and New York. Most people using either Windows or Mac have Microsoft’s TrueType core fonts for the Web installed on their machine these days, which means designers can specify Andale Mono, Arial, Comic Sans, Courier New, Impact, Georgia, Times New Roman, Trebuchet MS, and Verdana, and be reasonably confident that a majority of viewers will see their pages as intended.