Is it at all possible to modify the look of a site without touching PHP?

I cannot find any information on editing site layout by modifying any underlying HTML and CSS, both of which I know. I found the CSS file and know what to do with it.

I am having a difficult time understanding how to modify the layout and look of pages. I have reviewed several books and waded through a number of forums only to find general information about customizing the look of a zencart that requires a deeper understanding of whole platform than I have time or inclination to develop. PHP is a bigger frog than I wish to eat and am looking for assistance/guidance in reworking the layout, look and organization of my roommates site.

All I want to do is edit content and redefine the design of the site. I do not want to do any "re-programming" or editing of PHP files. Is there any WYSIWYG way to accomplish?

Any suggestions?

Warren Stiles
Sammamish, WA