toolkitscriptmanager

i use   calendarextender         of the           ajaxcontroltoolkit 
but when run  under the code ,come out mistake
 (function() {var fn = function() {$get("ContentPlaceHolder1_??????1_ToolkitScriptManager1_HiddenField").value = '';Sys.Application.remove_init(fn);};Sys.Application.add_init(fn);})();//]]>
warning message : microsoft jscript run mistake :'null' is null or is not mistake
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