We transitioned out of using TABLE layouts to fixed width floating DIVs around the end of 2004. With the rest of the industry we struggled with different browsers we struggled with fine tuning each div based on the container. Commonly one pixel could make the difference between a breaking on Internet Explorer, which would throw off a background color or a faux column.
In Early 2010 We started using Percentage width for DIVs inside the container. This method made it easier for us to layout websites. We no longer have to calculate inside widths and we maintain perfect ratios.
We've opened up the way we use this method to the world with a one page brief and some examples.
Read the full document at Perfect Percentage Grid (PPGrid)