(27) Understand the medium
Websites are very different to print, video and other media. You need to understand how. You can't always transfer your brochure to a web page. Spend time learning exactly how websites work, their strengths and weaknesses. Don't try and force your website to do things it can't. Take advantage of the things it can do.
(28) Don't be gullible
As a website owner you will be subjected to numerous special offers, pearls of wisdom and other nonsense. Learn to be a skeptic. See Domain Scams for more info.
(29) Be careful of time-sensitive pages
If you have a "Whats New" or "Latest News" page, either keep it updated or lose it. A stale time-sensitive page says to your visitors "This entire website is obsolete. You might as well leave now."
(30) Learn to read statistics
Statistics are the health monitors of your website. They don't just show you haw many visitors you have, they show you how well your site is functioning, identify broken links, help you know where to direct your efforts, and much more.
(31) Go easy on plugins
Only use plugins such as Java, Flash and media players if they are necessary, and if the site won't suffer too much for those visitors who don't have them installed. Provide alternatives if possible. Avoid making your visitors download an uncommon plugin - most people won't do it.
(32) Avoid popup windows
Although there is a place for popup windows, they are out of favour and many people block them. Only use them if you are very confident they are the best solution.
(33) Validate your HTML
Use an HTML validator to check your web pages.
(34) Create effective error messages
All sites experience errors. Even if all your links work, you will still have occasional "Page Not Found" errors (never mind why - just trust us). Learn how to create a custom error page (it could direct them to your home page or provide a search form).
If you use frames or plugins, some people (and search engines) will only see the error message. Make sure your listing in Google doesn't show your site description as "Sorry, your browser is unable to view this page".
Take control and make sure your error messages provide useful information and solutions.
(35) Don't publish "Under Construction" material
Few things are more annoying than making the effort to visit a page, only to find that it's not finished. If it's not finished, don't publish it. Also, remember that search engines could index your page and you may find yourself stuck with a listing that says "This page is under construction" for a long time - long after the page is actually finished.
(36) Make your site's purpose clear
Many designers forget that visitors may have no idea what the site is about. Spell it out. Don't be scared to say "This site is about..." or "Our company deals in..."
(37) Be honest
Never misrepresent your site's content, your personal details, or anything at all. You will get caught out and the consequences will be more dire than you think.
Never trick your visitors into doing anything. It will backfire.
Never try to fool search engines, even if you think you're genuinely being helpful. They already know all about your special secret trick. They are smarter than you and they will punish you severely.
(38) Have fun!
If you aren't enjoying your website, you'll get sick of it and give up. Websites are fun - love it!