mainbody in layout options doesn't work

hi i have a problem with the mainbody settings

link to website http://www.worldpersia.eu

can u please help
how can i set the with of the mainbody

Hi

In the screenshot You've attached there is an option to set mainbody width. It's pepared to best fit the size of mobile devices, so You cannot set the specific width with pixels, but You can choose to make it widther by selecting 2.5 for example.