Keeping Pop-ups in viewport

I am using a Superfish plugin to display menu pop-ups but the problem is when a menu item is big it gets overflow from viewport.

How can I adjust the position of pop-up menu to开发者_开发技巧 always keep it in the viewport.

I've helped someone turn superfish into a megadropdown and I think this may be a nice clean way to reformat your code with only HTML & CSS changes. Otherwise, I think you'd have to resort javascript/jQuery.