To illustrate, take a look at the following screen capture:
When you search using the search box at the top of the left sidebar, you will see the search results appear with a few tabs above them. Currently, we've set it up so you can see results from Math-Drills.com and MathShare.com. Simply click on one of those tabs and your search results will be filtered to only show results from the website you select.
If you want to see the results from the entire web, just click on "All" again. When you click on a link from the search results, your link should open in a new window, so you don't lose your place in the results.
We hope that you will find the new search functionality useful, and it results in finding exactly what you need. Of course, if you don't find what you need, please let us know and maybe we can make it.