<script type='text/javascript'>
            window.onload = initialize;
            function initialize() {
                var validate_isnumeric = document.getElementById("validate_isnumeric");
                validate_isnumeric.onclick = CheckNumeric();
            }

            function CheckNumeric() {
                var oErrorElem = document.getElementById("errorMessage");
                var oInputElem = document.getElementById("numOrText");
                if(!IsNumeric(oInputElem.value)) {
                    oErrorElem.innerHTML = "Invalid numeric input";
                    oErrorElem.className = "error";
                }else {
                    oErrorElem.innerHTML = "";
                    oErrorElem.className = "";
                }
            }

            function IsNumeric(sText) {
               var ValidChars = "0123456789.";
               var IsNumber=true;
               var Char;
               for (i = 0; i < sText.length && IsNumber == true; i++){
                  Char = sText.charAt(i);
                  if (ValidChars.indexOf(Char) == -1) {
                     IsNumber = false;
                     break;
                  }
               }
               return IsNumber;
               }
        </script>