How to update records from CRM web forms using javascript in MS CRM 4.0

function UpdateEntityRecord(entityName, attributes, orgName)

{

      //attributes = ?accountid> 92384923 ?/accountid>?firstname>harry?/firstname> ...

  var xmlString = "??sXml version='1.0' encoding='utf-8'?>";

      xmlString +="?soap:Envelope xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema'>";

      xmlString +="?soap:Header>?CrmAuthenticationToken xmlns='http://schemas.microsoft.com/crm/2007/WebServices'>";

      xmlString +="?AuthenticationType xmlns='http://schemas.microsoft.com/crm/2007/CoreTypes'>0?/AuthenticationType>";

      xmlString +="?OrganizationName xmlns='http://schemas.microsoft.com/crm/2007/CoreTypes'>" + orgName + "?/OrganizationName>";

      xmlString +="?CallerId xmlns='http://schemas.microsoft.com/crm/2007/CoreTypes'>00000000-0000-0000-0000-000000000000?/CallerId>";

      xmlString +="?/CrmAuthenticationToken>";

      xmlString +="?/soap:Header>";

      xmlString += " ?soap:Body>" +

      xmlString +="   ?Update xmlns='http://schemas.microsoft.com/crm/2007/WebServices'>";

      xmlString +="     ?entity xsi:type='" + entityName + "'>";

      xmlString +=  attributes;

      xmlString +="     ?/entity>";

      xmlString +="   ?/Update>";

      xmlString +=" ?/soap:Body>";

      xmlString +="?/soap:Envelope>";

      oXmlHttp.open("POST", "http://localhost/mscrmservices/2007/crmservice.asmx",false);

      oXmlHttp.setRequestHeader("Content-Type", "text/xml; charset=utf-8");

      oXmlHttp.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/crm/2007/WebServices/Update");

      oXmlHttp.send(sXml);

      

  var results = xmlHttpRequest.responseXML;

}

Please replace '?' with '<' after copying and before pasting..:)