Storyboarding is an idea borrowed from the film industry in which all the camera shots and scenes are roughly sketched out before filming.  This is a very useful technique to use for a web page. Storyboarding provides an overall rough outline of what the web site will look like, including which  topics go where, the links, and a conceptual idea of  where your graphics go and what the image will look like overall.

With that  representation in hand, you can develop each page in     turn without trying to  remember exactly where that  page fits into the overall scheme and it's often complex relationships.

You don't have to be able to draw to produce a storyboard. You need only sketch in the outlines. 'This image goes in the top right hand corner, this heading is level 2 and centered, this paragraph goes here etc. You can draw all this in simple shapes with a few notes. 'This page is a white background, the navigation links go
here and point to' and so on. You may even want to name the files you need for each page so you know which image or piece of
text goes where. You may need to provide examples of things like house style for copy and image style and size for graphics
to go with the storyboard.

Ideally, someone should be able to look at your storyboard, no matter how crude, and using the right material, put together the
same site you would have done. If you have a large site to develop this can be very useful, allowing you to farm out work to
others. From the storyboard they should be able to layout the pages as you want them. When you assemble the project you should have consistently designed pages despite having several different authors.