<Images Alt=” “> Tag – Use it wisely and you can quickly turn Images into Assets. Engines can’t index your image based only on what the image looks like – you need to tell them what the image is with text. The only indexable keyword aspect of images is the text of the page the image is on but most importantly the text you put in the <image alt=”put text here”> tag.
Use of the alt tag also is very effective in helping your images rank well in Search Engines Image Search, so it should NOT be ignored.
Bear in mind that you shouldn’t expect a big ranking boost from this tactic – in fact you may get none at all. Including image alt text is a optimization technique that even Bing suggests you use for better ranking.
Two more reasons for using the alt tag are:
1. When you make an image a link, the alt text functions as anchor text and can therefore influence the ranking for the target page similar to how text based anchor text works. Typically text links are regarded as better for this purpose, but if you have to use an image for your link, be sure to include the similar keywords optimized text in the alt text.
2. The latest HTML specs require that images have an Alt tag, failure to include this information will cause validation errors.
In essence, using the alt tag can sometimes help, and will never hurt your ranking and web design efforts. Therefore, you should use the alt tag whenever doing so holds any chance of making an image keyword-meaningful and thereby stacking the advantages in your favor.