When using a WYSIWYG editor in Joomla 1.5 to create website content I am not able to freely insert HTML tags, such as IFRAME as the HTML tags will be automatically removed on saving the article. I can either configure Joomla not to use a WYSIWYG editor which makes editing articles a bit of a pain, or I can force the HTML code into the article using MySQL Query Browser and altering the article content directly in the site's database. Doing this is not only cumbersome but also ineffective, because every time someone edits the article from the Joomla back end WYSIWYG editor, the inserted tags will be removed by the editor again.
Short answer: no. Joomla knows best :P
But seriously, you can turn off the WYSIWYG for just your user. Go to the 'User Manager', select your account, and set the 'User Editor' preference to be 'Editor - No Editor'. That way you can type in whatever tags and code you want, without WYSIWYG borkage. But every other account on the site will still have access to their WYSIWYG's.