When WYSIWYG editor is used in a Joomla site and you use subdomains, you should be careful with setting your live site global variables, because the Joomla page uses $mos_Config_live_site to load the java script of WYSIWYG editor.
In order to protect you against potentially malicious scripting. IE only allows script from your domain to run on it's page. If you didn't specify the correct subdomain in the configuration.php file for your joomla site, you may have the following error:
Error: Access is denied.
Normally, in linux system, your website files will be located in the "www" folder, whose contents correspond to the "www.yoursite.com" domain name. So if you install joomla in a subdirectory called "myJoomla" under "www", you should configure $mos_Config_live_site="http://www.yoursite.com/myJoomla" for your IE users.
According to Joomla Forum , this problem does not exist for firefox users because firefox considers folder-domain and sub-domain to be matched.