CSS: Fix positioning for relatively positioned 'body'/'html' elements

Special thanks for @sporkmonger for the original idea.

Fixes #491
Fixes #423
Fixes #200

Ref #495
Flash: Added a new 'error[name=clipboard-error]' event

This event fires after the aftercopy event but before the click bubbled event.
It is only fired if errors occurred in Flash during the clipboard injection.

Fixes #245