TBH: I do not do very much php/html work (actually, very little verging on none ;) ); however, I'm a curious person and do a lot of reading, I came across the following article some time ago and I think it may help you, I could be wrong, but it shouldn't hurt either:
Learn CSS Positioning in Ten Steps
There is a tabbed tutorial here, and on the right side, a little box that shows what happens with each of the positioning types
and how the potentially affect each other!. I know for this, I was a visual learner; thus, having the effect of each type shown was most helpful.
Here's another site I use for reference on things SQL; however, it has a lot of other tutorials, one of which is:
CSS Layout - The position Property
between one of these two sites hopefully a solution to your question is available.
Once you have it, please post back - even if it's close, if you will post the script, someone here may be able to help tweak it. Remember to format posted script using the
[CODE/] formatting tool.