In rare cases your AllWebMenus menu might be some pixels away for a specific browser. Thus you need to apply to this menu the appropriate x,y offset values for this browser only. In other words you need to apply in your menu browser specific offsets.

To do that you just have to click on the "Menu Positioning" button. In the window that will appear you must click on the "Click for Browser-specific offsets" button and define properly the offsets for the specific browser (see the image below).

Finally, recompile your menu and re-upload the appropriate files if you have it (i.e. the menu) online.