Hoople - 7:33 pm on Jul 20, 2013 (gmt 0)
Been there, done that with the above. A point to remember is older versions of IE misbehave re 'box model' - read and reread online about how to avoid triggering 'quirks mode' to save lots of grief.
A second point to also keep in mind is these older versions have issues with rounding up/down (errors) and for that matter, how they handle decimal precision.
I personally compensate by making all the box parameters add up to not quite 100%. This allow for a bit of sloppiness in the browsers' results of rounding, esp if the actual 'space' exceeds 99.8% of what you've allowed for in your design.