function checkfirstpage() {
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  var screen=0;
  var man = 0;
  
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
    if (pair[0] == "screen") {
      var  screen = pair[1];
    } else if (pair[0] == "man"){
	   var man = pair[1];
	}
  }    
    if (screen==0 && man==0 ) {
    alert("This is first page");   
	return (false);
    }
}

function checklastpage() {
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  var screen=0;
  var pg = 0;
  
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
    if (pair[0] == "screen") {
      screen = pair[1];
	  screen++;
    } else if (pair[0] == "pg"){
	   pg = pair[1];
	}
  }    
    if (screen == pg ) { 
    alert("This is last page");
	return (false);   
    }
}