Say you are using one style sheet for an entire site, but you want the same elements to have different style for each page what should you do? Well you could give each of those elements a different class, but that’s not very efficient. A simpler way is to give the body of each page an ID. Then you can use descending selectors to style each element. So for instance if you want the h1 to look different on on the contact page then on the home page you would do something like this:

body#home h1 {color:#EEEEEE;}

body#contact h1 {color:#000000;}

It’s pretty simple, but can be very powerful.