If you Google image search for “search engine differences”, you’ll find a chart I made as the first result for a post I did a while back. The small matter of whether anyone is even searching for “search engine differences” (especially in the Image Search) doesn’t matter at the moment. What does matter is that I optimized that image for that keyword phrase:
<p><img class="aligncenter size-full wp-image-602" title= "search engine differences" src="http://www.maine-seo.com/ wp-content/uploads/2009/02/search-engine-differences1.jpg" alt="search engine differences" width="522" height="511" /></p>
WordPress gives images a title tag when you give it a description, and one of the SEO plugins I use adds the alt tag you can see.
What’s the point?
You should use alt tags. Since traffic these days comes from every direction from email newletters, direct traffic, and good ol’ web searches to blog, image, and video searches it’s necessary to optimize for every possible avenue.
So, use keywords and phrases where you can; but by effectively describing the image. Rich talked about Matt Cutts’ video on this a few months ago.
Why you have to be careful
When you look at your Analytics, image searches may often skew the results. Take a look at this blogs traffic sources – Google’s image search is number 6!
But, when you take a look at how long those people spent on the site, it’s only an average of :22.
If these stats are negatively affecting your Analytics, you can set up a filter like you would to block your IP address to block traffic from Google (or other search engines) Images.