I change the width with both CSS and PageStructure but it didn't change

Hallo,
I have a problem with the page width. I have changed it by:
General > Forum > Configuration > Page Structure

and

by changing the body's CSS

but it won't work.

Wee.. it works for the header

Spoiler:

but doesn't work for the body

Spoiler:

Can you help me ASAP? Some member has protested about the page layout and I don't know how to handle it anymore. I have searched over this site and only found those ways above to fix it but they don't work.

Hello,

Try using this CSS code for width..

Code:

#wrap {
width : 800px !important;
}

I have added it but... it didn't change.

I tried to change my friend's forum, it works. But why it doesn't work on mine? I have changed the skin for several times but, again, there's no change. I've change the all style and there's no change.

Any other suggestion...?

Please provide a link to your forum.