var er = true;
var name = document.getElementById("name");
var email = document.getElementById("email");
var phone = document.getElementById("tel");

function validate_form()
{
er = true;
check_empty(name);
check_empty(email);
check_empty(tel);

if(invalid_email(email.value))
{
email.style.border = '1px solid red';
er = false;
}
else{email.style.border = '1px solid #ccc';
}
if(er) {return true;}
else return false;
}
function check_empty(field)
{
if(field.value == ''){ field.style.border = '1px solid red';
er = false;
}
else{ field.style.border = '1px solid #ccc';}
}
function invalid_email(email) {
   var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
    if(reg.test(email) == false) {
    return true;
   }
   else return false;
}