I don't know if this is specifically a Mac Pro issue but since Safari is the only browser I have this problem with I figure it can't hurt to ask. I use a lot of browsers and often have a lot of tabs open in each of them. Safari does something every now and then that none of my other browsers do. When I switch between tabs or click somewhere in a tab Safari will sometimes randomly open the tab in a new window. I am absolutely positive that I did not hit anything to purposely open the tab in a new window. It drives me bananas when this happens but I can't find a solution to it when I search online. Thoughts? Help? Advice?