How to use the alternative text attribute
The Alternative text (alt text) attribute is a text eqivalent of an object or image that describes the content and function of an image, this is useful for anyone with a visual impairment, or if a screen reader is being used. Alt text can also be very useful when an internet browser does not support the format of the image.
The alt text is either within the alt attribute (tag) or alternatvely adjacent to the image or within the same web page.
On most browsers when you hover over an image a small box will display the alt text.