penders - 3:17 pm on Jun 30, 2010 (gmt 0)

From a recent thread in the HTML Forum [webmasterworld.com]:

tedster: As to what the search engines will use, that is always a question worth watching and testing. Right now the alt attribute is what affects ranking, from what I can see, and the title attribute is not used as a signal. And that makes sense, because it is what non-visual browsers and screen readers like JAWS will be "reading" aloud.