I need to compare two sites say X and Y. Both X and Y are the same websites, but in Y we made some changes in a particular stage. So I need to verify the changes by comparing X and Y. Can you suggest some tools to identify the changes in my page?
If this is for professional development, then your version control system should diff the files for you. If you have no version control, then shame on you ;-)
In any case, if the websites were remote, you could use you could use HTTrack to download them.
Since you say that you made changes, then I presume that you already have them locally. In which case, the answer is simple.
Then, for each file, you can compare the two versions and see the differences (even copy sections from one to the other):
I think that that will solve your problem (and, please, consider using version control in future ;-)