Saw this...http://html5.org/tools/web-apps-tracker ... 13&to=6914
...and came to this...http://www.w3.org/TR/html5/webappapis.h ... ipt-errors
Secondly it would be exceptionally useful if the onerror event emulated PHP's error handling. A function name and perhaps a back-tracking ability (what called what, did function a1 call b2 and b2 spawned the error? etc).
Having these two issues covered by the spec would greatly improve error handling.