ZydoSEO - 10:53 pm on Nov 11, 2012 (gmt 0)
Phranque is correct. There is a big difference in how Google treats a 302 and 301 redirects. Yes, the "user" gets to the same place, but it's different from Google's perspective, and how they affect rankings. Hell, a meta refresh would also get the user to the same destination but it doesn't mean it's a smart thing to do from an SEO perspective.
A 302 redirect says essentially, "Index the 'content' located at the page's new, temporary location but associate it with the old URL." The old URL is not deindexed. And the new URL can ALSO get indexed if other inbound links directly to it can be found. Now you have duplicate pages accessible under the old and new URL. And credit for links pointing to the old URL are NOT transfered over to the new URL. Say the old URL had 100 inbound links and the new URL also acquires 100 inbound links. As a result of using a 302 redirect, Google is going to see this as two URLs (each with duplicate content) with 100 links each.
A 301 on the otherhand tells Google that the page at the old URL has moved permanently, so they will transfer credit for the old URL's backlinks over to the new URL. If the old URL has 100 backlinks and the new URL has acquired 100 dirct backlinks of its own, the new URL will be given credit for 200 URLs, not 100 (as it would for the 302 scenario above).
And yes it takes several weeks typically for 301s to be processed. You have to wait on the engines to recrawl EVERY inbound link to the redirected URL, discover the 301 for each individual inbound link, transfer credit 1-by-1 for each link as they recrawl them individually. Depending on how often the sites that link to you get crawled, this could take days, weeks, or maybe even a month or two.
If you're using 302 redirects instead of 301s when pages are moved or deleted, you are creating duplicate content and split link equity. The results of doing so are essentially the same as URL canonicalization issues. Not a great idea IMO.