In Safari versions up to 5.x, there was a SnapBack button sitting at the far right in the URL bar. When you searched and clicked on a link in the results list, you could navigate further from site to site and still quickly return to your earlier search results. That button is gone in Safari 6 on Mountain Lion.
But the good news is that the SnapBack feature is still available; only, this time you’ll use a keyboard shortcut, which is even better. If you type Command-Option-S, the SnapBack feature will take you back to search results just as in the “old days”.