need style sheet help

I need help with this style sheet.
I'm basically trying to do layout with css as opossed to tables. But I'm having trouble.

Can someone explain why the layout on this home page isn't working?

readefrat.com

The class selector just doesn't seem to match. Why not?

Here is relevant stylesheet;

/*
text block selectors
*/
H1
{
font-family: arial;
font-size: 50;
}

H3
{
font-family: arial;
font-size: 24;
}
/*
page structure selectors
*/
BODY.first
{
background-color: #6633FF;
text-align:center;
}
BODY.FIRST DIV
{

margin: 20;
background-color:#FFFF00;
width:500;
height: 300;
}
BODY.ARTICLES
{
margin: 15;
background-color: red;

/*
collumn positioning classes. "right" and "left" can be used to divide an area into
two equal collums. They can be used inside the the "two thirds left" classed division
to make a three collum layout. These can be used seperately or together for
internal header and footer layout as well as division of collums on the start page.
*/

.one_third_left
{
width: 33%;
float:left;
}
.two_thirds_right
{
width: 65%;
float: right;
text-align: left;

}

.left
{
width: 48%;
text-align:center;

}

.right
{
width: 48%;
text-align:center;
background-color: blue;
}