Change Width of iWeb Navigation Bar ?

Hello All,

I am new to iWeb and have very limited experience with HTML. I had seen in an on-line tutorial of iweb how to change the page width, (i.e the default is 700 px and I'd like to change it to 1000 px). Is it also possible to change the navigation bar also to 1000 px width? I can't seem to figure out how to do this.

Thanks for your help in advance.
K