The script tags should contain "defer" attribute. Resolution: You can set the LoadScriptsBeforeUI property of the script manager to false so that the scripts will render as late in the page as possible (just above the inline <script> that MS AJAX generates for the $create() statements). This will provide benefit nearly identical to the defer feature, but it does not risk breaking existing functionality. More information on the property: https://msdn.microsoft.com/en-us/library/system.web.ui.scriptmanager.loadscriptsbeforeui(v=vs.110).aspx