Storyboarding

"A graphic outline of a multimedia project in which each page represents a screen to be designed and developed." (source)

Include BOTH an overall structure (describing navigation) and a detailed sketch of each unique page. (For pages that are essentially the same layout and function, you can use just one sketch.)

Here's a graphic showing how: http://ritter.tea.state.tx.us/technology/techapp/images/storyboard.gif

Here's some links that might be useful:
http://www.cwrl.utexas.edu/~davis/crs/309/storyboarding.htm
http://www.conquerorwebdesign.com/seo-romania/website-storyboard.html
http://www.amacord.com/services/storybrd.html
http://e-articles.info/e/a/title/How-to-Storyboard-Your-Web-Site/
http://www.mcli.dist.maricopa.edu/authoring/studio/guidebook/storyboard_example.html

An example: http://aaahq.org/TeachCurr/newsletters/Fall00/storyboard.gif

Use your judgment as to how detailed to make the storyboard. Obviously, a simple webquest storyboard will be pretty simple, right? For a webquest, maybe use the attached template to help you storyboard. 

To see some examples:
http://images.google.com/images?q=website+storyboard&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&ei=OKRtSuOmKILONfT2jfkG&sa=X&oi=image_result_group&ct=title&resnum=4

NOTE:  you don't have to be this elaborate:  http://library.creativecow.net/articles/val_mark/3d_toon/storyboard.jpg.  That's more for a STORY, or film rather than a static web page. 

Aim for something like this:  http://www.boardofstudies.nsw.edu.au/syllabus_hsc/img-ipt/storyboard.png.

You can use this template to describe each unique screen: http://www.mcli.dist.maricopa.edu/authoring/studio/guidebook/sb.html