Here is an idea to test whether people quickly understand what your website is about. See the full article at http://www.uie.com/articles/five_second_test/:
Show users a full content page for 5 seconds to get their initial impressions
1. Show users a content page. Once the users views it for 5 seconds, cover it up or change the window
2. Ask them to write down everything they can remember about the page
3. Ask them questions like, "What is the most important information on this page?" or "How would you go about completing task XYZ?"
You can understand how clear/concise your page was, whether users understood the primary purpose of the page, whether users recalled the critical information, etc.
The 5-second test can be done quickly/cheaply using paper prototypes, however, it's best for pages where there's a single primary purpose (rather than a homepage, where there might be multiple purposes).