a problem about django-grappelli

[Scarl]

After I use django-grappelli, the admin site looks very nice. 

But when I enter /admin/diary/day, and add something, it looks terrible. It shows left side only! 

I want it to expand the width of website. How to do it?

The follow picture is my admin site. I also want it to expand the width.

https://code.google.com/p/django-grappelli/wiki/screenshots

This is what I want!

Please tell me how to do it. Thx!