As mentioned earlier (repeatedly), web pages are nothing more than
text and references to files and directions where to place those files
(images) into a web page. In the "early" days of web pages, graphic
images were a luxury and it was often desirable to see a web page with
nothing more than the text and a reference as to what picture would be
seen, should that be desired. With slow modem connections to the
Internet, it was often wise to turn off images and get the information
needed in text form. To allow for this, web browsers had the ability to
choose whether or not to load images. If a browser came to a page
with images but had been told to turn images off, it would display some
text in place of the image. This text is known as Alternate Image
Tags.
There are other uses for Alternate Image Tags. When you load a page that is graphically intense (many and/or large numbers of graphics), you may have noticed that sometimes words appear before the images appear. These are the Alternate Image Tags and they often appear while the graphics are loading
Also, if a web page is accessed by a visually impaired person, they may have the web page "read" to them by the computer. If that is done, images will be "referenced" verbally by the Alternate Image Tags.
To add Alternate Image Tags to a web page, you can add the text when you add the image or after you have the image in place. If the image is already placed in your web page, click on the picture and pull down FORMAT>Image Info (or you may double-click the image). Then in the Text box, enter the alternate information and press OK as below.
As additional information, the Alternative Representation box (above)
could be used to select a low resoultion image to display while a better,
higher-resolution image is being loaded.