A couple of fonts were designed primarily to display on screen, and so tend to look good, whilst some others designed in a more traditional manner, and then turned in to bitmaps, don’t always look impressive. Verdana & Georgia are amongst the bitmap-designed fonts, and should give fairly sans-serif and serif fonts respectively. As Kunal said, you should write your css rules to work through from the fonts you would most like, to the generic families that make sure you’ll get something like what you want. An example might go:
body {
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 80%
}
This means the browser should work through from the first to the last font, displaying the first one listed that is installed on the machine.
The font-size bit isn’t necessary for choosing fonts, but can be useful if you want to make a layout with dimensions based on font sizes, to allow for easy rescaling (see
http://www.alistapart.com/articles/elastic/ for an article about this, with links to a nice demo on the
http://www.csszengarden.com site.)