I work in an environment of Visual Studio 2013 C # aspx ie10 See the attached project. After pressing the Send key twice, I get the message below. The control ID is generated automatically by Rad. Thanks in advance KAMARA YAIR Email KAMARA.Y@LAVIETIMETECH.COM Exception details: Unhandled exception at line 15, column 9936 in http://localhost:53353/Telerik.Web.UI.WebResource.axd?_TSM_HiddenField_=RadScriptManager1_TSM&compress=1&_TSM_CombinedScripts_=;;System.Web.Extensions,+Version=3.5.0.0,+Culture=neutral,+PublicKeyToken=31bf3856ad364e35:he-IL:eb198dbd-2212-44f6-bb15-882bde414f00:ea597d4b:b25378d2;Telerik.Web.UI,+Version=2014.1.403.35,+Culture=neutral,+PublicKeyToken=121fae78165ba3d4:he-IL:64f74e2d-5497-4ab7-8321-89bccc22f4bb:16e4e7cd:86526ba7:874f8ea2:f7645509:24ee1bba:e330518b:1e771326:88144a7a:8e6f0d33:6a6d718d:ed16cbdc 0x800a139e - JavaScript runtime error: Sys.WebForms.PageRequestManagerServerErrorException: Multiple controls with the same ID 'ctl02' were found. FindControl requires that controls have unique IDs.