[support] display html tinymce

Hi, I'm running Drupal 7.12 and I'm quite lost. When I create a page with the tinymce wywiwyg editor, the text won't appear with the parameters, only the html code is displayed. I tried to create new text format but no luck. For example when I write "Essai" in bold and in the middle of the page I have on the result : <h2 style="text-align: center;">[b]Essai[/b]</h2> I'm not using html tag limitation. Any Ideas ?