Readability is probably one of, if not the most important aspect of a web site's design. After all, what use is your site if it's an eye sore and no one can bare to look at it? Here are a few tips to help improve readability
Just like each monitor and screen resolution may display things slightly different from one to the next, not all of us can see the same colors. Too many designers don't even take color blindness into consideration when choosing colours to use. Personally, I like to use the Colour Contrast Check by snook.ca and the Color Scheme Designer 3. Used in combination, both tools make colour choice a breeze.
Let's face it, no one wants to spend time reading a verbose wall of text. Get to your point quickly and keep verbage to a minimum.
Use appropirate spacing in text. The general rule of thumb is to take the line height, divide by the font size and aim for a value of 1.5.
Stop putting those stupid ads in the middle of your posts. There is a place for advertising and in the middle of a post is not one of them. Most viewers do not want to see ads at all, let alone in the middle of something they are trying to read.
DON'T USE ALL CAPS - nuff said.
Break paragraphs up as much as possible. Unlike the standard 4-5 sentances per paragraph on a physical document, web paragraphs should contain 2-3 sentances. Avoid the walls of text that scare off readers.