$(function(){
    $("[name='email']").focus(function(){
        if ($(this).val() == 'enter your email address') {
            $(this).val('');
        }
    });
    
    $("[name='email']").blur(function(){
        if ($(this).val() == '') {
            $(this).val('enter your email address');
        }
    });
});

function checkEmail(){
    var email = $("[name='email']").val();
    var pattern = /^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/;
    if (pattern.test(email)) {
        return true;
    }
    else {
        if (email == "enter your email address") {
            alert("Please enter your email address.");
        }
        else {
            alert("Please enter a valid email address.");
        }
        return false;
    }
}