如何让twitter引导子菜单在左边打开?

I was trying to create twitter bootstrap submenu in dropdown menu, but I've got a problem: I have dropdown menu in the top right corner of the page and that menu has one more submenu. However, when submenu opens - it does not fit in the window and goes too much to the right, so that user can see only first letters. How to make that submenu to open not to the right, but to the left?I was trying to create twitter bootstrap submen