Function Ajax (data) {createxmlhttprequest (); If (Data = Document. getelementbyid ("username") {XMLHTTP. Open ("get", "user_ck.php? Username = "+ data. value, true); document. getelementbyid ('username _ notice '). innerhtml = process_request; // display status} else if (Data = document. getelementbyid ("veruserid") {XMLHTTP. open ("get", "user_ck.php? Veruserid = "+ data. value, true); document. getelementbyid ("veruserid_notice "). innerhtml = process_request; // display status} else if (Data = document. getelementbyid ("verify") {XMLHTTP. open ("Post", "veruser_check.php", true); XMLHTTP. setRequestHeader ('content-type', 'application/X-WWW-form-urlencoded'); document. getelementbyid ("verify_notice "). innerhtml = process_request; // display status} // "checkcode =" + checkcode. value + "& User Name = "+ XMLHTTP. onreadystatechange = function () {// alert ("Zhong"); If (4 = XMLHTTP. readystate) {If (200 = XMLHTTP. status) {var responsetext = XMLHTTP. responsetext; responsetext = responsetext. replace (/(^ \ s *) | (\ s * $)/g, ""); If (responsetext = "true") {ck_user (data, "True") ;}else {ck_user (data, "false") ;}} else {alert ("error occurred! ") ;}} If (Data = document. getelementbyid ("veruserid") | DATA = document. getelementbyid ("username") {XMLHTTP. setRequestHeader ("If-modified-since", "0"); XMLHTTP. send (null);} else if (Data = document. getelementbyid ("verify") {XMLHTTP. send ("veruserid =" + document. getelementbyid ("veruserid "). value + "& veruserpwd =" + document. getelementbyid ("verpassword "). value );}}