Suppose someone asks the group about the effect of sleep on psoriasis. In this case, there might be too many hits, so find a way to narrow the search. It's a bit more helpful than just pointing a new arrival to the archive, and the URL isn't likely to be so long that it breaks by wrapping in the newsreader. It redirects an abbreviated query off to the chosen search engine, and is designed to be called with a search string. URLs cannot pass certain characters such as blank spaces .
Some sites have the frame removed to prevent nesting frames or where it's deemed inappropriate.