[tigerb]

1. As THTx says, it's good to be using stylesheets for just such an occasion. It is definitely worth the time and effort to get all your webpages using stylesheets, because it makes all sorts of global changes possible with fairly little effort -- it's the classic case of more time spent up front leading to scads of saved time later.

2. In general, sans-serif fonts have been found to be more readable on the screen than serif fonts. Serif fonts like Times and Georgia are pretty good for big headers, but not for paragraphs of text. Most people recommend Arial or Verdana for a body text font. (Trebuchet also has some proponents.)

3. Your default font size probably shouldn't be any smaller than 10pt, if your contrast is good, or 12pt, if the contrast is less good. Many people like to use relative type sizes in their stylesheets, so if you set the basic paragraph font to 10pt, then had headings that were 120% of that, you could later change your mind and switch to 12pt with very little work.