Cell Padding Using CSS on an HTML Table

I need to pad just one cell in my table. I gave the td element a class and de开发者_如何学JAVAfined the class in my CSS file like this

.itemQuantity
{
    padding-right:30px;
    text-align:right;
    background-color: #EEE;
}

Padding-right does not seem to be doing anything.

I changed the css to

td.itemQuantity
{
    padding-right:30px;
    text-align:right;
    background-color: #EEE;
}

Now it works.