The alt attribute, or tag, (Alternative text) is used in HTML & XHTML documents to specify the text description of an image.
Alternative text is useful for people with low bandwidth connections, who may set their browser to not load images or for people using handheld devices or using a pay per transferred data connection.
Other uses include people with disabilities who use assistive technology, such as refreshable braille displays or screen readers.
Search engines can read the image ALT tag to determine what the image actually is because as we all know; search engines cannot read an image.
In the early years of web development alternative text was helpful as people often used text-only browsers (like Lynx), and still today, alternative text is still highly appreciated by users with accessibility requirements & users looking for ways to optimise their website.
The alt tag is mostly referred to as an image "alt tag".
Its intended use is not to provide pop up text or tooltips when a user's mouse hovers over the image, its intended for supplementary information that can be used in this way.
If the image is not important, you can simply use an empty atl tag, some will use (*).
Often the ALT tag is abused in web design as some stuff it with keywords and key phrases to try to gain a higher listing within the search engines, fools.
