JQuery Offset Error

I was working on a drop-down menu that was fixed at the top of the page. It worked in Firefox, but not IE or Chrome. By using the developer tools in Chrome I discovered that there was an error on getting the offset position. The error message was "Cannot read property 'tagName' of null" and was being caused by the jQuery dimensions plugin. This plugin was used by the previous menu and wasn't needed any more so I removed it and the drop-down menus worked!