Difference between ID and CLASS

[mumford1]

Hi

I ahve seen a few style sheets now that use classes such as div id="maincontent" what is the difference in using id as oppose to class

also what is number character for between div and container
below

DIV#container {
MARGIN: 1em auto 0px; BORDER-LEFT: black 1px solid; WIDTH: 770px; POSITION: relative; BACKGROUND-COLOR: #e6eef7
}

thanks alot

[TheOriginalH]

Divs are effectively unique - not reusable enitities, whereas classes are "types" of area's, and can be recycled.

The Hash/Number/Pound symbol is identical in function for divs as the "." is for classes...

ie:

div#container {
}

represents the values of the div named container (so you'd use <div id="container"> just as,

.container {
}

could be used for <span class="container">

[slider]

When H says div, substitute id and you'll get what he means...

A class is reusable. An id is not. On any page you can only have one div with an id of id1. But you can have as many div's with a class of class1 as you want.

That's the main difference.