Google removed frame from search results pages on Google Video, that Google used to display both external site and a list of related videos, instead of direct link to the original site. This duplicated the functionality from video sites like YouTube, while making it difficult to navigate and to share a URL.
Google Image Search uses a similar frame, but it's more useful as it provides information about search results. If you don't like the frame from Google Image Search, you can use Greasemonkey scripts like Google Image Relinker or Google Image direct links to bypass it.
Source:→ Google System