More data, this time an inadvertent experiment or two.
I was cleaning up my web site and noticed that my logo, which is at the top of the page had an obsolete alt-tag, which was put on about 3 years ago. There are at least 20 pages from 1 to 3 years old that had this alt tag. Since the logo is at the very top of the page I thought that it might be indexed.
So I did a quick search on Google and Altavist for the phrase, and neither had
In these pages there was no link on that logo. On another image there was
a link to our homepage and the phrase is indexed.
I did another search that was sure to pull up the page with the logo,
including a word that should be highlighted in the logo alt tag. It wasn't.
My conclusion is still that non-linked alt tags don't count for much in Google.
Even when searching for images using words out of the alt tag didn't bring up the logo.
It may be that if you have too many words in the alt tag it isn't used to index the
image. (this has 6 words)
So I can't understand results that vary!