var isOK;
var errMsg;

function validate() {
    errMsg = "";
    isOK = true
    errMsg = "Please enter: \n \n";
    vName();
    vEmail();
    vQuestion();
    {
        if (isOK == true) {
            return true;
        } else {
            alert(errMsg);
            return false;
        }

    }
}
function vName() {
    if (document.forms[0].elements["txtName"].value == "") {
        errMsg = errMsg + "Your Name";
        isOK = false;
    }
}

function vEmail() {
    var email = document.forms[0].elements["txtEmail"].value;
    if (email != "") {
        var expn = /\w{2,}\@\w{2,}\.[a-z]{2,}/i;
        if (expn.exec(email) == null) {
            isOK = false;
            errMsg = errMsg + "\n" + "A valid email address";
        }
    } else {
        isOK = false;
        errMsg = errMsg + "\n" + "Your email address";
    }
}

function vSubject() {
    if (document.forms[0].elements["txtSubject"].value == "") {
        errMsg = errMsg + "\n" + "Subject of your Query or Comment";
        isOK = false;
    }
}

function vQuestion() {
    if (document.forms[0].elements["txtMessage"].value == "") {
        errMsg = errMsg + "\n" + "Your Question, Query or Comment";
        isOK = false;
    }
}