consider an abbreviated version that does no loading, just resolves and checks assertions
perhaps use Duff's Device http://home.earthlink.net/~kendrasg/info/js_opt/jsOptMain.html#duffsdevice
Document which algorithms allow mutating function arguments.
Determine whether attribute global namespace is done with getAttributeNS('', n) or getAttributeNS(null,n)
Opera want the 'px' or not?
For browsers that support iframe onload, do the events bubble up? does returning false help?
incorporate any ideas/code from http://code.audiofarm.de/Logger/ (written in ActionScript 2.0)
maybe let bu_debug and so on be used in burst_first after all
How does load() handle a non-existent or unreadable file?
Can you attach handlers to document.documentElement?
Make has_window_event_listener return true for opera 7.5?
When will IE throw a synchronous error to load()
Any escaping of the string in case it has xml in it?
Does mozilla have a useful return value from DomDocument.load()?
What does either IE or Moz do with a "file:" url? Is it still async?
Support the xml and http mechanisms available through Flash (XML.sendAndLoad(), etc.)
Consider Konqueror W3 "Load and Save" support.