Yes, of course it will help your images get ranked for the keywords contained in the alt attribute in Google image search.

The alt is best for seo and google image purposes whilst title is good for usability as when people mouseover the image the title content will show in the browser.

The Alt Image attribute is completely ignored by google unless the image is clickable as a link, then it takes the place of anchor text and carries weight for both the anchor page and the target page as it falls into the 'bridge' position.

Anyone not knowing what the 'bridge' position is ask & i will explain it.

Are you sure it's ignored? I thought they used it for Google Images?

Bridge? Go on then...

May wanna have a look at this as well : Matt video: ALT attributes for images

I was replying to the question asked which related to SEO "how people do this for SEO, placing". I will state again the alt text is ignored fr SEo weighting unless the image is a link. I am not talking about image search usability etc etc, I am stating a reply to the original question.

Also, if you watch what Matt Says, he says 'we understand what the image is about', the image, not the page etc.

I think its more like using keywords in your website's text, it might not get you good ranking on its own but its good to use them nonetheless. Obviously google recommends (Make sure that your TITLE tags and ALT attributes are descriptive and accurate.) using them and they're good from user's point of view as well, so why not use them.

OWG is right, the Alt is used in Google Image Search, but not in Search Ranking for organic search results. Don't forget that Alt is an abreviation for "Alternative" intended to be an alternative for the picture itself. It should therefore go somewhere towards describing the content of the picture or graphic.

For example "Large red Widget with circular flange"
OR
"Logo for the Widget Makers Trade Guild"
and so on.

Don't forget accessibility problems for the partialy sighted who may be using an audio browser. Just imagine how it must sound to them when every picture is read out as a bunch of concentrated Keywords. Then there is the Accessibility legislation itself to comply with such as in the UK there is DDA Compliance to take into account.

Now as Firefox and some other browsers don't display the Alt as you mouse over the image, but do display the "Title" it has become comon practice to use the previously much ignored "Title Attribute which was mainly ignored in the past. Consequently, the image Title is often a direct Copy (or slightly rewritten version) of the Alt.

OWG i would like to know more about 'bridge' position which you have denoted above. As you said above please make one thing more clear and it's the impact of Alt tag is ignored by Big G and only considered when making the image as a link.

Means only when we use any image as a link to another page with Alt attribute is covered by google.

Amit