function flipHeaderLogin(obj) {
	if (obj != null) {
    var val = obj.value;
    if(val!=''){
			obj.style.backgroundPosition = '172px';
		} else {
			obj.style.backgroundPosition = '0px';
		}


  } 
}

function checkLoginInputs(){
	flipHeaderLogin(document.getElementById('header_username'));
	flipHeaderLogin(document.getElementById('header_password'));
}