Look and Feel

Does the design send a clear message about the company? (e.g., “We’re high-tech, cutting-edge, technology-oriented,” or “We’re conservative, solid, trustworthy,” or “We’re funky, whimsical, off-the-wall.”)
Does the message sent by the design match the product?
Does the design feel clean and balanced, or cluttered and confused?
Is there a clear color palette?
Does the design suddenly change on any of the sub-pages?
Does the site load reasonably quickly?
Avoid using tacky clip-art animations.
Avoid over-used color palettes (e.g., red/white/blue)
Avoid centering
Avoid using more than two fonts
Avoiding using serif and sans-serif fonts on the same page (unless you’re really good at it)
Avoid having large areas of light text on a dark or black background
Avoid large areas of italicized or cursive text
Avoid over-large or all-caps text that SHOUTS at the viewer
Avoid long pages where the viewer has to scroll through many screens
Never make the viewer scroll horizontally

Navigation/Site Architecture

Is there global navigation appearing near the top or left side of every page?
Is there a hyperlink version of the global nav at the bottom of every page?
Is the navigation simple and easy to understand and follow?
Are there more than eight or nine nav buttons? (If so, consider switching to a drop-down menu.)
As you navigate through the site, is it always clear where you are and how to get back home?
Does each page have a title, and is it the same as the title in the navigation?
Are there any broken or non-functioning links?
If a link takes you off-site, can you get back by closing the new window or do you have to back-track through several pages using the browser’s back button?
Are there multiple tiers of pages (i.e., pages with sub-pages which have further sub-pages)? If so, consider using a “breadcrumb” tracking system so the viewer can always retrace his steps.
If it’s an e-commerce site, is the shopping cart simple, and easy to use?
Does the viewer receive a message reassuring him that the site is secure?