var emailfilter=/^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i

function checkform(form){

if(form.name.value==''){
    alert("Please enter your name.");
    form.name.select()
    return false;
}
var returnval=emailfilter.test(form.email.value)
if (returnval==false){
    alert("Please enter a valid email address.");
    form.email.select();
    return false;
}
if(form.problem.value==''){
    alert("Please enter message.");
    form.problem.select()
    return false;
}

return true;
}