I have a Mac and Safari 5.1.3 on OS 10.7.3 but this has done this for a long time. When I click on 'Forum tools' the three options are blank until I mouse over them then the text such as 'mark as read' appear. Not sure if this is a site issue or a Safari problem. Thanks.
It actually only does this on 'forum tools'. When I click on 'thread tool' or anything else they all appear.