Cross browser testing using QTP11

[jahmed2345]

I have my Web application automated in IE8 with QTP11. I want to do a cross browser testing and see how the application behaves in Mozilla and Chrome.
I spent quite a lot of time on different forums (and cross browser testing related threads on this forums), but I still have following doubts and I feel this is the best place to get a guidance.
1. What is actually meant by Cross Browser testing? What somebody means when he says “How the system ‘BEHAVES’ on different browsers? What are the behaviors I actually need to look for?
2. I am using completely descriptive programing in  BPT framework. I am not using OR at all. If I run the same script in different browsers, wil my object properties change? Will I need to make huge changes in the script?

So you can see I am not getting a lead to start with.
Please help.