My slight modification on this is:

    data:text/html,<html><head><title>Notepad</title><style>html,body{margin:0;padding:0;}textarea{padding:10px;font-family:Courier;font-size:16px;height:100%;width:100%;border:none;outline:none;}</style></head><body><textarea style="height:100%;width:100%;font-size:16px;padding:10px;"></textarea><script>document.getElementsByTagName('textarea')[0].focus()</script></body></html>