Display accesskeys, mostly harmless

Variation of the Keyboard shortcut display for web pages by Jason Barnabe (np).
This version tries not to affect layout, so the letters ale displayed in simple bubble of fixed dimensions[2)] next to its elements [1)] and disappears while hovered/focused.
Test it here:
http://eldar.cz/myf/pub/firefox/accesskeys-test-area.html

Notes:
1) I've found, that for now (in FF2.0) it is not possible to add CSS-generated content after any INPUT (of any type), TEXTAREA , and image-map AREA. Possibly a bug or some conflict between form elements binding and rendering engine(?). [4)]
2) Dimensions absolutely relies on used font. This versions expects "Courier new" (present on Windows platform). Other fallback fonts may cause few pixels difference. Then you must tweak last three lines of the first ruleset containing font-size and margin-left. Use the testing ground linked above.
3) Not using "*" selector for 'better performance'. Naming all four remaining accesskey-ready elements explicitly.
4) I wrote a simple workaround userscript (and enhanced version of this userstyle) that physically adds accesskey letters after inputs.
Supportive userscript: http://userscripts.org/scripts/show/8376
Enhanced userstyle: http://userstyles.org/styles/2193

Known issues:
1) Wrapping links with accesskeys are forced not to wrap. It is necessary in order to be efficient in case of short single-line links in narrow fixed-width columns. Delete this rule (it is the last one in the source) if it destroys something.

Changelog:
2007-10-14 + opacity, screenshots (taken from last.fm)