Hello.
I noticed that if I try to insert a new link on a text, and the text is located in the lowest part of the screen, the pop up window appears below the visibile area and, consequently, is not visible (unless you scroll down the browser bar, of course). For usability reasons the displaying should be fluid (and flexible): if there is not enough space below, the pop up should appear above (or elsewhere).
It is an important issue, because the user should be always put in a position to understand what is happening. :)