function clear_input(input_id) {
 document.getElementById(input_id).value = "";
}

function showhide(layer) {
    if (document.getElementById(layer).style.display == "block") {
    document.getElementById(layer).style.display = "none";
    return;
	}

    if (document.getElementById(layer).style.display == "none" || !document.getElementById(layer).style.display ) {
    document.getElementById(layer).style.display = "block";
    return;
    }
}

function check_select(select_id, layer) {
 if (parseFloat(document.getElementById(select_id).value) == -1)
 {
  showhide(layer);
 } 
}