If you are using tables entirely for page layout, I just have 2 tips for you.
The first one is that:
Don’t rely on rowspan or colspan.
Especially on pages with potential to get rather long or wide by the help of some elongated table cell with rowspan or colspan. Things might very possibly go wrong in IE, which cannot be solved by CSS but only restructuring of the holy tables.
Table layouts are a nightmare to debug and recode. It’s already too much trouble, so you’d not want to spice the problems up by tweaking them up more. Attributes rowspan and colspan can be tricky under many circumstances, and in almost all cases, you can work out the same effect by creating another table in position.
Another tip is:
Tables with only a single row or a single column or even a single cell work the smartest in table layout design.
Use as simple table structures as possible. Stack and nest them up but make them stay simple. Don’t count too much on any one table, he’ll definitely get icky.