General Practice of using icons
Generally we have seperate icon file as image for an icon. I take and example lets say I have 10 icons on my page so 10 icon images in my application. there Images are embedded in page of css to display icons.
What is the problem in existing approach
Well From the functionality point of view there is no problem. Icons/images are the resources resides on application server .
I assume the hosting server is IIS in our case .When our page is loaded it asks for the icon images from the server and it provides those . IIS can parallely provide only 2 resources at a time (it could be css files , script file or image files or any other resources ). So for 10 images we need minimum 5 request to the webserver and this means longer response time.
How Icon set help
Idea of using iconset is pretty simple .We keep all out icons in one file (assuming we have defined dimentions of icons if not you need to fix those.)and than use these icons via css.Now we have only one file as icon so there will be iconset image file will be served and some other resource also be served to the browser.Now we have speed up our response time by minimum 5 times .
my icon set image looks like this
And on my page it look like this
Download sample from here