After sketches, the usual next step in Web design is creating wireframes.
A wireframe is essentially a schematic diagram of a page. Typically, it shows where different kinds of content will go, the relative prominence of things like headings, and the navigation devices like menus and search.
HOW YOU TEST IT:
You test a wireframe by making up tasks, usually all related to navigation: “How would you find _____?” “What would you expect to see when you click on this link?”
Wireframe tests won’t take very long because there’s not a lot people can do with them. You’ll usually do them in a session which includes testing of other things, like your existing site or other people’s sites.
WHAT YOU GET OUT OF IT:
The main thing you’re testing is your categorization scheme and naming: Are things where people expect to find them? Do the category names you’re using make sense? Is it clear how the navigation is supposed to work? You may find, for instance, that you’ve organized your site according to your org chart and users don’t think that way.