Check this image: http://img301.imageshack.us/img301/8296/aaec3.jpg. This is a div within a html table. I want to force that div to have no space with the browser's border. How can I do?

try

body
{
    margin: 0;
    padding: 0;
}

Yup, but try to suppose I have this div into a table with a cellpadding 2. Is there a way I can force this div to have margin: 0 even if it's whitin the table?

The div will have zero margin, its the tables cell padding that will mess it up for you, you would have to set cell padding to 0

You can also use a container div but you would still have the same problem if you use tables.

Best thig to do is not to use tables for layout, why would you want to put a div inside a table - your making things hard for yourself and overly complicated, use css for layout and tables for tabular data, you can style the table in the css stylesheet.

Putting divs inside of tables is a lot like wearing shoes inside your socks.

That's becouse I'm on vBulletin, which is created with tables.
Anyway, I have solved by adding zero margin to the table.
Thank you for your replies.