In more detail, edwin ...
Each subsite has a "master" template associated with it. By changing this you can change the look of all the pages associated with that subsite as Jun points out. You're restricted to
- Things that can be handled by CSS style pages (each master can refer to or build its own style sheet)
- "wrapper" stuff like the header at the top of the page, navigation panels on the side, footers on the bottom, or "newest news" panels, that kind of thing. All package content will then be put inside whatever wrapper HTML to specify in your template master.
In the current version of the toolkit packages have an unfortunate tendency to emit their own headers and context bars rather than set them up for the subsite master to fiddle with (or leave out, in some cases). Fixing this by massaging the package template structure is on my list of things to be fixed on 4.6 if we can find a volunteer to do it.
Even as things stand today, though, you have a lot of control over the look and feel of your site through the modification of subsite master templates (the main site is just another subsite that happens to be mounted at "/")
Install and play with the "skin" package. It demonstratess how you can change the look and feel between three simple (demo-quality) themes.
Also the new portal package, which will be in 4.6 but is not in 4.5, supports theming at the portlet level.
