Problem in my javascript validation

function mainvalidation() {
            alert("1");
            var select_time = document.getElementById('<%=SelectTimeZone.ClientID %>');
            var select_grade = document.getElementById('<%=DropDownListLevel.ClientID %>').nodeValue.toString();
            var select_area = document.getElementById('<%=DropDownListArea.ClientID %>').nodeValue.toString();
            var select_subject = document.getElementById('<%=DropDownListSubject.ClientID %>').nodeValue.toString();
            var uemail = document.getElementById('<%=TxtEMailID.ClientID %>').nodeValue.toString();
            var uname = document.getElementById('<%=TxtName.ClientID %>').nodeValue.toString();

            if (select_time == "" || select_time == "Select Time Zone") {
                alert("Select Time Zone");
                return false;
            }
            
            if (select_grade == "" || select_grade == "Select Grade") {
                alert("Select Grade");
                return false;
            }
            if (select_area == "" || select_area == "Select Area") {
                alert("Select Area");
                return false;
            }
            if (select_subject == "" || select_subject == "Select Subject") {
                alert("Select Subject");
                return false;
            }
            if (uname == "" || uname == "Enter Your Name ...") {
                alert("Enter Your Name");
                return false;
            }

            if (uemail == "" || uemail == "Enter Your e-mail ...") {
                alert("Enter Email ID");
                return false;
            }
            var emailPat = /^(\".*\"|[A-Za-z]\w*)@(\[\d{1,3}(\.\d{1,3}){3}]|[A-Za-z]\w*(\.[A-Za-z]\w*)+)$/
            var EmailmatchArray = uemail.match(emailPat);
            if (EmailmatchArray == null) {
                alert("Your email address seems incorrect. Please try again.");
                return false;
            }
           }

var select_time = document.getElementById('<%=SelectTimeZone.ClientID %>');