The width of the output modules in the "top"

Hi!
I need to get four modules in the "top" position. But we need to deduce three modules with a width of 33% and, and the fourth with a width of 100%. All four modules are HTML- code.
Now all four modules are output with a width of 33%. Three in the first row and Fourth in the left in the second row.
How can I do that?

Hi

Please tell me the url to the exact page with an example of this issue.