css layout breaks in firefox when table added

[c_developer]

I created a simple layout in scc using divs and css:

*********************
* header *
*********************
*left * right *
* * *
*********************

all are within a container div setting width
header has width defined
next, left has a width defined and uses float: left
the right div is then listed

It displayes fine in both firefox and IE, UNTIL I ADD A TABLE anywhere in the body of right, or anywhere on the page!

Sudennly, Firefox does not honor the layout - it is as though table code breaks its recognition of div layouts.

What am I doing wrong? Where is a good example of basic css layout I should be following that will not break?

(It is not an answer to say do not use tables - understand they are being used in the CONTENT on the right, for data displayed in a tabular format, as tables should be - not for layout. When I add them, again, the layout is broken).

Thank you

[icantthinkofone]

Can't help without the complete code.

[c_developer]

I fixed it - added a div around the left and right with a clear:both. DOn't know why but it works. Thank you.