var testresults;
function checkemail(email){
	var str=email;
	var filter=/^.+@.+\..{2,3}$/;
	if (filter.test(str)) testresults=true; else{
		testresults=false;
	}
    if (!testresults) alert("Please, enter correct e-mail address!");
    return (testresults);
}

function checksearch(text){
	testresults=true;
    if (text == "") testresults=false;
    if (!testresults) alert("Please, fill in the search string and choose at least one chapter!");
    return (testresults);
}

function showalert(){
  window.document.getElementById('grid').style.display = 'block';
  return false;
}

function hidealert(){
  window.document.getElementById('grid').style.display = 'none';
  return false;
}