LoginAction.do file where it comes from? stuck

I m stuck in some jsp programing issue. I'm working as temp web-admin for my friend who is one vacations. I'm managing his freelance web-designing website. Over the weekend i was told by my friend ; to make changes in the login.jsp page and do some programing to log user credentials in a file.

I have edited the action field in login.jsp and diverted it to my log.jsp ; the file logs users credentials reading it from username / password field and saving it into a file. This works perfectly in my test-webserver but when i run into his production server it just throws the page to loginAction.do. There is nothing in the login.jsp page to tell it to go there.

I try to google jsp made files and i see this file lot common. Is it a built-in function or routine. I try finding it on the web server directories but couldn't locate it

I want to know what action is promoting this behavior. I'm new to this web-server admin ;

Kindly help me guys.