codice:
<script language="javascript">
		function ValidaForm(jvs_IDAreaVendita) 
		{
			var no_errore = 1;
			var jvs_form_valido = 1;
			var jvs_elenco_errori = "";
			
			//alert ("Valido il form")
			
			//alert("jvs_IDAreaVendita:   "+jvs_IDAreaVendita)

				//Valida UserName
				var objUserName
				objUserName = document.getElementsByName("UserName")

				if (objUserName[0].value.length < 6)
					{
						document.getElementById("lblUserName").style.display='block';
						jvs_form_valido = 0;
						jvs_elenco_errori = jvs_elenco_errori + "\n" + " Enter a valid UserName"
					}
				else
					{
						objUserName = objUserName[0].value.toLowerCase();
							//alert ("User name:   "+objUserName)
						var ValidaUserName = CheckStringaAlfaNumerica(objUserName)
						if (ValidaUserName == 0)
						{
							document.getElementById("lblUserName").style.display='block';
							jvs_form_valido = 0;
							jvs_elenco_errori = jvs_elenco_errori + "\n" + " Enter a valid UserName"
						}
						else
						{
							document.getElementById("lblUserName").style.display='none';
						}
					}
			//alert ("Fine validazione form:  "+jvs_form_valido)
			if (jvs_form_valido==0)
				{
				alert(" ATTENTION!!!" +jvs_elenco_errori)
				}
			document.Int_returnValue = jvs_form_valido;		
		}

  </Script>
così è OK!!