Using document.domain breaks SharePoint’s menus
The following is a repost from my old SharePoint blog: http://vspug.com/kwanl/2007/02/09/using-document-domain-breaks-sharepoint-s-menus/
If you have some script in your web part page that sets the document.domain to a parent domain you will find that the SharePoint menus (Modify Shared Page, web part menus) inexplicably stop working.
I thought you may be able to get it to work by resetting the document.domain to the original value but this is not allowed. Although, doing this anyways gets the menus to work again but I noticed other scripts stopped working.