1) A suite is often better because you can easily run all tests. In an IDE, you can do this by selecting the package. A suite lets you do the same in Ant though. Take a look at Classpath Suite so you can use wildcards rather than listing out each class one by one.
2) Not built in, but you can write a small amount of code to do so. Here's an example of setup before a suite and tear down after a suite. The only disadvantage is that you are running as a main method rather than via a junit runner. No green bar. (Built in you can run code before and after a class, but not a suite.)
I'm testing 3 websites. each one consists of many pages. in this test:
1. should I test the trivial things (header, sidebar link) in every pages or just once in the main page?
2. I'm using eclipse, so should I use a separate package for each page and separate projects for each websites?