Web Site Preferences
You can set the Web site style used here. Select the preferences you want below. As you change a preference, you'll see a preview of how pages will look in the preview frame. When you're satisfied with the look, press the Save button to set the preferences for the entire site. The page will refresh to allow you to see the style you selected; if you don't like that style, just select another one and press Save.
As a contributor, you have additional controls. The donation sections on the pages are off by default, but you can turn them on if you want. (No, I don't know why you'd do this. The main Donation section is easy to find. Consider it a test of future capabilities.) You can also turn off the display of ads if you want. I keep them on by default, even for contributors, because ads can be interesting; if you disagree, turn them off.