The most important factor of a web site is that it should be easy to
read. After all, it’s intention is to educate the user on the benefit of
your product or service over it’s competitors.
You should choose
your text and background colors very carefully. You don't want to use
backgrounds that obscure your text or use colors that make your text
hard to read.
Select your font type and size according to your
page layout, using small font sizes allows you to fit more content on
the site but makes the text harder to read. Keep in mind that monitor
resolutions are increasing which also makes the text difficult to read,
especially if you are targeting older audience.