Various browsers have trouble with the tab character used in the Text Formatting Rules. If you can't type a tab, or if you are fixing up a page written by someone who didn't type tabs, then you should have us convert spans of spaces to tabs for you. You request space to tab conversion with the checkbox that appears near the bottom of Edit Text and Edit Copy pages. It looks something like this...
[ ] I cannot type tabs. Please Convert Spaces To Tabs for me when I save.
A span of spaces must be at least three spaces long to be recognized as a tab. Use multiples of eight spaces to make multiple tabs. Each span of eight spaces will convert to one tab. If the last span comes up a little short, that's ok, as long as there are at least three spaces in the last (only) span.
Check your work. This sort of Heuristic Rule can lead to unexpected results: for example if the page you edited contains formatted code, it might well happen that ConvertSpacesToTabs messes up all the formatting.
See Tip For Typing Tab for help with getting tabs into text when your browser is fighting you.
[Maintenance note: This page is seen when the user clicks on the "Convert Spaces To Tabs" link on any edit screen. It describes what happens when you ask the system to do this, why you would want it to, and ways to avoid the spaces-instead-of-tabs problem.] I wonder if Text Formatting Rules would be better on any edit screen; I guess other common problems would be better too. -- Andrew Cates
Q: Tabs are no longer necessary for bullet items. One or more asterisks at the beginning of a line are sufficient. However, some seem to keep converting them back to tabbed versions. Is there more to the story?
See also: Improving Convert Spaces To Tabs, Convert Spaces To Tabs Not For Code, Wiki Tabotage, Convert Tabs To Spaces, Tab Munging
See also: ajaxian.com 
for a related Java Script discussion.
See original on c2.com