Realize the event on the web page which was loaded in browser.

For example, when i go into page: www.google.com, after the web page finished loading, I want to know the actions from the user to the objects on the web pages such as button, text box..., for example, when we click to the text box, message will show "the user has just clicked to text box." actually, I want to get the pass in the password textbox on gmail?, I use hook to capture keystrokes but I don't know when to start to hook, :( hjx

ah and not server realize, I mean user realize. When the website loaded, user can disable network but website is still in browser,
I mean when I click mouse to a textbox on that website, is there any way to realize that click event ? I'm creating a project C# to do it but I don't know method
p/s: My English is not good, i wish you know what I mean, thankss :)