Enable spellchecker of browser by default
Firefox got a custom spellchecker which can check the content of textareas automatically. The Problem is that this feature is being disabled by tinymce on default.
I don't know the correct way to fix it. A workaround (and to test this feature) add the following line
$code = str_replace('"reAddCss":"true"}', '"reAddCss":"true","gecko_spellcheck":"true"}', $code);
in class.tx_tinymce_rte_base.php in function parseConfig($config) before the return statement