Text Considerations
Don't use text that is too small to read.
Don't use huge font sizes. (Don't yell at your visitors.)
Don't crowd text up against the left edge.
Don't stretch text across the width of the entire page.
Don't center text in paragraphs.
Don't type in ALL CAPS.
Don't type paragraphs in bold print. (That's also the same as yelling!)
Don't type paragraphs in italics.
Don't type paragraphs in ALL CAPS, bold, and italics all at once.
Don't underline text unless it is a link.
Other considerations
Don't use "Under Construction" signs on a page full of information. Everyone's pages are currently under construction! By all means, don't have a link to a page that just says "Under Construction" with no other content.
Don't use images or icons that are unrelated to the content or what the button does. In other words, make sure there is a connection.
Don't forget to use ALT tags on images.
Don't use huge, unoptimized images that take forever to load.
Don't steal someone else's graphics. If you use it you should get permission first.
Don't use a background that interferes with the message, text or other information on the page.
Don't forget to provide webmaster information on at least the home page.
Don't use anything that even looks like an advertisement!
Don't use scrolling, blinking, flashing text or images all over your page.
Don't use pop-ups in most instances.
Don't play music without offering a way to turn it off.
Don't use hit counters. Who cares? Use site stats instead.
Don't tell me the time and date. I have it at the bottom of my screen.
After your site is published, it is important to keep the content current. Most good sites are constantly updated, so if yours is out-of-date, users won't return. If your site has static material, users won't need to return as it appears they saw all there was to see the first time. This is true even for large sites.