margin problems

I noticed today my page has different size blue margins depending on what computer (or browser?) it’s being displayed on. Some have no margin and it’s all page. It should have about a two inch blue (background) margin on each side. Is that what you see?

Question, how do I make sure the same margin is there for everyone who visits the site? Is it thier browser, or is this something I can control?

My site: http://www.losangelessoccer.org

[duplicate: http://ww.wp.xz.cn/support/topic/never-get-answers?replies=4 ]