Choosing Effective Alt Tags

What is alt tag?  To put it in simple term, it's a way of naming an image in text with keyword or keywords.  A client of mine asked us to make her website friendly to the blind because she's a big advocate for the blinds.  She wants all of the images on her website to have an alt tag in it.  Little did she knows that she asking us to optimize her site for search engines because search engine is blind to the image unless it's alt tagged.   As a webmaster if you have ever attempted to validate your site without the use of alt tags you have discovered your results will return the error required attribute  ALT not specified.Alt tags were designed to provide alternative text for images to visually impaired individuals who access the net through audio based browsers. They will also provide alternative text for individuals who have disabled image loading in their browsers.  Research indicates that some search engines spiders appear to see and use alt text as content when indexing your site. In terms of SEO techniques, it is important to carefully consider this fact when selecting alternative text for your images.

Example of a proper alt tag:
<img border="0" src="seo.gif" width="457" height="115" alt="SEO">  A responsible webmaster or site owner will not abuse the use of alt tags but should certainly be aware of what effect the choice of text will have on search engine results. Caution should especially be taken on images located at the top of pages such as headers that appear on every page of your site. The use of identical alt text at the "top" of every page could very well destroy all the work you have put into optimizing your site. 

Many web designers use transparent spacer gifs and decorative images, to help with the layout of their design. Although all images need an alt tag, these types of images should always use an empty alt tag. Do not even consider hiding key words in the alt tags of these types of images.  Notice in the example below, that the quotation marks for an empty alt tag are located directly next to each other with no space between. This will allow special screen readers designed for the sight impaired, to ignore this type of tag. If you did not use an alt tag for these images, the user would hear the word image for each missing tag.