Hi , I have followed the following steps from here : https://support.mozilla.org/en-US/questions/1190923. To have windows open as tabs , this always worked fine up till today for some reason. Now when i have this set i get the error ' a web page is slowing down your browser. What would you like to do ? " When i refresh Firefox and disabled the modification the window pop up and load fine , its just when they are force to tabs is where they give the error. I deleted the cache and cookies and done the processHang solution and few others and still no joy. Just wondering is there any solution to this. Thanks in advance.