To call some javascript before the postback event is raised, use the following code: if (!Page.ClientScript.IsOnSubmitStatementRegistered(type, “script_onsubmit_editor_” + ClientID)) {   string popTextareaScript =      “var ed = YAHOO.widget.EditorInfo.getEditorById(‘” + editor.ClientID + “‘);”      + “ed.cleanHTML();”;    Page.ClientScript.RegisterOnSubmitStatement(type,       “script_onsubmit_editor_” + ClientID, popTextareaScript); } In the above code example I was trying to populate a textarea from the YUI Editor.

Know More