Pixel Border and Percentage width in Proportion

Question

I think I might already know the answer to this one but I need a sanity check!

Say I have

#gridtest{
width:590px;
}

I could change the

Answer 1

You could use an inset box-shadow instead of a border:

box-shadow: 0px 0px 0px 10px red inset;

Just pad the inside of the container to compensate.

Edit: I write "pad" but of course if you use padding it'll throw off the box dimensions. Margin the content inside instead.