Never used ismap attribute in image tag ever.
Referred http://www.w3schools.com/tags/tag_img.asp and it says
Specifies an image as a server-side image-map. Rarely used. Look at usemap instead
Since I'm a front end web developer, I may not have opportunity to use it.
Could any serverside guys please shed some light on it?
You specify a map file as a target for an anchor containing the ismap image. The map file then defines target areas so that clicking on the image will take you to different pages depending on where you click.
This tutorial (the instructions are slightly IUPUI-specific, but the basics aren't) clarifies things a bit.
usemap is preferred though, I believe - see this tutorial for an example of that.