Here's a summary of some web design reminders that all webmasters should know, yet sometimes get overlooked in all the haste and details of building a website.
1) Design sites so they look and work properly on all browsers.
2) Design sites so they look and work properly at any resolution.
3) Be sure your sites still function and look right if a css call fails.
4) Be sure your sites still work when security-conscious users disable Java, Flash, scripting, etc. in their browsers.
5) Be sure your sites still look and work right if embedded objects fail (or are blocked per point #4 above). Don’t rely too heavily on plug-ins and widgets. Use trinkets sparingly for highlights, not the majority of basic content.
6) Keep your clients focused on their customers, not themselves. Gently remind them that the website isn't being built for their own amusement or to impress their buddies or competitors, but for their customers, future prospects, the public, or whatever the case really is.