JavaScript " null " and "undefined"

JavaScript :

I need to check if every object is null or undefined - if neither, I must proceed with the validation. Else, Javascript throws ugly errors on the screen.

Check for null

if(object!=null) // the object isn't null.

Check for undefined

if(object) // the object is not 'undefined'

JavaScript DOM

I just discovered that JavaScript DOM does have some problems - I ran into problems doing the cross - browser testing. Apprarently, some part of the code didn't work in Netscape & Mozilla.

E.g; IE recognizes the parentElement keyword but Netscae wants parentNode.

I need to scrouge the net for a compatibility list.........