An annoying condition whereby different browsers or editors insert and/or replace tabs with spaces or spaces with tabs (possibly without user's knowledge), harming the alignment/indentation or wiki-processing of fixed-pitch text examples, such as code listings and AsciiArt.
Various partial-workarounds are often used to reduce the damage caused by this process. This tag may be used to indicate that such workarounds were undertaken in an effort to explain why there may be some odd characters or other curious artifacts.
Please Don't Remove Prevention Characters - Sometimes special symbols are put in place to prevent or reduce TabMunging. In some cases someone has come along and "repaired" tab problems and removed such symbols. However, as explained below, repairs are often temporary as someone's browser/editor may inadvertently mess it up yet again. I realize those characters are ugly, but they are the "least of 2 evils". Thanks.
I have recently experienced this (see EditingReallyBigPagesWithLynx) in that, although ViEditor has no trouble with tabs, when the edit is complete, the resulting text passed back to Lynx has the tabs converted to spaces.
Haven't yet figured out how to suppress that automatic conversion.
Even if you do figure it out, it takes only one bad edit from somebody else to ruin the tabbing. Your editor may be wonderful, but if a different person with an editor set wrong edits the topic, bammo! It reminds me of nulls in string concatenation for some languages: one null can bust the entire string. It is a "weakest link in the chain" principle.
I usually use periods as space-holders for illustrations, but some seem to prefer under-scores. The problem with underscores is that they often make the example look like an input form, which is misleading in some contexts.
The worst case I've seen of tab munging is in the Toad stored procedure editor. So much so that I abandon tabs often to use spaces.
See also: ImprovingConvertSpacesToTabs