HTML ALT Image

When an HTML image cannot be displayed (because, for example, you might have provided a broken URL) the browser will show the alternative 'alt' property. 

HTML Example:

Result:

Some browsers will display the ALT text when you hover over the image. You will find this property particularly useful for users with text-only browsers (like Lynx) or visitors with very slow connections (like GPRS) who have turned images off. 

Using the alt property is also good for SEO purposes. Search engine spiders cannot read images and, with the 'alt' text, you can help them "understand" what the image is about. Google Images will index your picture properly and it will appear under the right search query.