How do you guys debug a webpage...

[jbv]

Hi list,
How do you guys debug a webpage that doesn't behave the same
way (especially js scripts) when opened in a browser and in
revBrowser ?
More specifically my problem is with xmlhttp.send which I have
used zillions of times, and which works fine in my webpage in
a browser and seems to throw an error when opened in revBrowser...
IOW is there a way to catch the error (or display js console
in revBrowser) ?
Thanks in advance.

jbv