Ya you need to be more specific, anything you prefer over the other? As CrazeD said, we need the answer to those questions first.
If you are revamping a website, and not totally redoing it or creating it from the ground up you won't really have a choice but to use the language the website is in now. If you are able to do the website over from start to finish I'm a fan of Flash. I just enjoy being able to have that dynamic look to a website and really having few boundaries when it comes to interaction with the website visitor.