function EnableEdit(){    var editor;    editor = document.getElementById("HtmlEdit").contentWindow;  // 针对IE浏览器, make it editable    editor.document.designMode = 'On';    editor.document.contentEditable = true;  // For compatible with FireFox, it should open and write something to make it work    editor.document.open();    editor.document.writeln('');    editor.document.writeln('');    editor.document.writeln('');    editor.document.close();}