Screenshot of the Global Configuration title bar

globalconfig-textfiltertab-thumbClick on image for an expanded view

Any one that can contribute content to your site, whether it be extensive articles, modules or just comments on the Front End is provided a text box of some sort in which to enter the content.  It may be a simple unadorned text box or a WSYWIG editor, depending on how it is set up for that group. There are a series of default settings for each User Group, and additionally the Text Editor that you use may have some of its own settings.

The filtering of these text elements helps keep your site secure and keeps people from entering things that you don't want at that level.

No HTML: means that the user can't use any HTML tags that could format the text, create divs, etc.  What they enter is pure text, like in Notepad.  If the user were to insert HTML tags such as <strong>, these tags will be removed when the entry is saved.

Default Black List: This means that this user group can enter limited HTML tags, but not use any that could be destructive to the site such as embeds, iframe, etc.  In the yellow box at the bottom of the page you will se a list of the Black Listed HTML tags.  You can add additional tags to this list in the Filter Tags area.

No Filtering: means that the HTML does not have any filters placed on it.

Other Things to Consider...

If you are using a WYSIWYG (what you see is what you get) editor, such as TinyMCE or JCE Editor, you may have to go into the controls for that component to change settings there. Often the default settings on these editors won't allow HTML tags and may have other restrictions. There may be times when you want to add <script> tags, such as putting in GoogleAds or for spot functionality on that page. In this case you need to enable that feature in the controls.

If you add additional groups to your Joomla site, the new groups will show up on this page as well. They will inherit the settings of their parent group. For instance, you create a group that has a parent of Registered, the group will automatically have all the settings that Registered has. In this Global Configuration screen, you can change the specific text filters for that specific group and override the settings of its parent group.