if you have a text area with some text in it, if you click a spot in teh center of the text area and then drag down to select text, when the mouse pointer reaches the edge of the text box, the selection highlight will wrap around as if the mouse pointer was above the first line of the textarea.
Created attachment 21606 [details]
video capture of the bug
I should also note that I have observed this behavior on both QtWebKit and Gtk WebKit.
Created attachment 21607 [details]
just a simple html file with a textarea and some text to use for testing.
*** This bug has been marked as a duplicate of 12593 ***