I am trying to send a user name and a password through url, for example I am login inn in a page using the text field provided in the page but actually sending those username and password to another site where its used to log in.
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What's your question or the problem you are having?
I'll try to guess at what it is you are after, but my answer will be nebulous.
Some servers will try to accept alternate arguments in the URL itself for instance when you see:
Tells the server to pass
Others use GET/POST statements to communicate below the user-level, so a user never sees the arguments passed. This is often the case with HTML forms where the method is set to Get|Post.
If your goal is to have a 'mock form' on a website that autofills in credentials for you (kinda sneaky if you ask me!) then you'll want to look at the receiving end to see how they want it passed to them. My guess is that most modern websites have deviated far FAR away from passing parameters in the URL as a form of authentication (as this is often clear text and violates basic security protocols). As such, you'll probably be doing a GET method where you request information back from the server based on credentials you've provided in a form. Start there.
If you want a more specific answer you'll have to provide a question or problem.