You've given us no information whatsoever to help you. I am browsing this site using IE 11 and I don't have any issues. Further, I use a lot of mojo site and have no issues with IE 11.
The best place to look is in your site's CSS. Press the F12 key on your keyboard after loading your site in IE 11; this will load the IE Developer Tools which you can use to find the CSS rule which causing all of your content to be centered.
Please give us some details so we can help you.