Table problem in Firefox and Explorer

Hi,

I’ve built my site using a twenty eleven child theme.

I have a quite strange problem.

My site has a fixed width of 1000px. I have created a table with 1 row and 5 columns. I assigned the width to each single cell, in this order:

300 | 50 | 300 | 50 | 300

This way I could insert an image in each of the “300px” cells, and keep a fixed space of 50px between them.

Now, problem is that in Chrome everything works fine, instead in Explorer and Firefox the “300px” cells (and their images) are ok but the “50px” are misteriously “shrinked at about, 20px … this way the final result is not centered but aligned to the left border.

Any idea about what’s happening?

Many many thanks in advance.

A.