URL is automatically added with $ _GET parameters after an AJAX request

I have the following source:

$('#loginnow').click(function() {       
    var login_useroremail       = $('input[name="login_useroremail"]').val();
    var login_password          = $('input[name="login_password"]').val();

    $.ajax({
            type: "POST",
            url: "http://www.example.com/login.php",   
            data: {
                login_useroremail: login_useroremail,
                login_password: login_password              
            },
            dataType: 'text',
            success: function(data) {       
                if(data == 'ok')
                {
                    alert('Registration successful!');  
                }
                else
                {
                    alert('Registration failed. Try again later.'); 
                }

            },
            error: function(data) {
                alert('Registration failed. Try again later.');
            }
    });     
});

I know that these warnings and conditions are unpleasant, but since I am in an early state of the project, I will clarify this later .;) I work with jQuery, jQuery Mobile and PHPTAL.

When I call the example and the login really succeeded (= the server returns "ok"), all this is finde.

My question is: Why, when I call the example and the login is not satisfied, are parameters automatically added to my URL bar? After the call, it looks like this:

www.example.com/index.php?user=blah&pw=yadda&...

Sometimes it also has a binding like

www.example.com/index.php#ui-state=dialog

At least I can imagine what it is for, I think it helps to remember what you are doing now in the mobile application.