function validate() {
        var valid = true;
        var errorMsg = "";

        var phoneAcRef = document.getElementById("phoneAc");
        var phoneNpaRef = document.getElementById("phoneNpa");
        var phoneNxxRef = document.getElementById("phoneNxx");

        var failureBoxRef = document.getElementById("failureBox");
        var failedItemsRef = document.getElementById("failedItems");

        if ( (phoneAcRef.value.length != 0) && (phoneNpaRef.value.length != 0) && (phoneNxxRef.value.length != 0) ) {
                if (!checkPhone(phoneAcRef.value,phoneNpaRef.value,phoneNxxRef.value)) {
                        valid = false;
                	errorMsg += "<li>" + "Mobile Number is not valid." + "</li>";

                }
        }
	else {
		valid = false;
               	errorMsg += "<li>" + "Mobile Number is required." + "</li>";
	}

        if (!valid) {
                // set errors
                failureBoxRef.style.display = "";
                failedItemsRef.innerHTML = errorMsg;
                window.location="#failureBox";
        }
        return valid;
}