Suppose I'm given the requiremnt to geneate a few pages that have tables on them. The original requirement is for all tables to be 500px.

I'd write my CSS as follows:

table
{
    width: 500px;
}

That will apply accross the board for all tables. Now, what if they change the requirment so that some tables are 600px. What's the best way to modify the CSS? Should I give the tables classes so

table.SizeOne
{
    width: 500px;
}

table.SizeTwo
{
    width: 600px;
}

Or is there a better way for me to deal with changes like this?