When you look at the usability of an entire Web site, I want to propose that there are five levels of it. From widest to narrowest, here is what I dub “The Five Rings of Usability” (man, I love making up important sounding names for stuff...)
Site Existence At the risk of being absurdly basic, this is the question of whether or not to have a Web site at all. Is the theme and gist of your site necessary? Realistic? Is your Web site solving a problem or addressing a need?
Site Content So, you’ve decided to have a site, great. Now, what goes in it? This is the decision of what content you publish. If you’re creating a support site for your product, do you post the product manual? Do you have an “About Us” page? A “Contact Us” page?
Information Architecture So, you have a site and you’re posting your product manual. Awesome. Can anyone find it? Information architecture is how your information or organized throughout your site. Is your stuff in places where people expect it to be, or do they have to hunt for it? Do you’re site move the user from content to content naturally, or laden with frustration?
Page Layout Fantastic, so we have a site, with good content, and it’s organized well. How does your actual page look? A Web site being a collection of individual, discrete pages, how is each of them organized in the browser? Does your header take up half the screen? Is the menu where people expect to find it? Do you have contact information in the footer of every page?
Individual Page Elements Finally, we get down to individual page elements. We have a site with good content, organization, and layout. But are your hyperlinks the same color as the surrounding text? Is your font size too small? Your date pickers, do they suck? Do your headings have the same amount of whitespace above them as below them?
Starting from the outer ring – the question of whether to have a Web site at all – it becomes a narrowing process, which each ring getting a little more specific. Getting them all lined up together is the trick.