Created attachment 58950 [details] test case In general, we treat clicking in the margins of an element as not clicking in that element for the purposes of text selection. So clicking in the margin to the left puts the selection at the beginning of that element and clicking in the margin to the right puts the selection at the end of that element. In general, I think that's correct, but the body element is an exception since it's the top-level visible element. It's easier to see this in the attached test case that what we currently do is clearly not what any user would expect.
The current behavior is consistent with Firefox 5, but Internet Explorer treat margins as if they are paddings.