DelimiterFlashTime is an option for cells that determines the time in seconds an opening delimiter flashes when its matching closing delimiter is entered.
With the default setting DelimiterFlashTime 0.3, matching delimiters flash for 0.3 seconds.
Delimiters include parentheses, brackets, and braces, as well as [[ or ]], (* or *), and paired special characters such as or .
With the setting DelimiterFlashTime 0, delimiters do not flash.
If you enter an unpaired closing delimiter, the standard Mathematica front end will beep.
You can use the front end menu command Edit Balance to select ranges with balanced delimiters in expressions.
You can set DelimiterFlashTime at the level of a single cell, a notebook, or the whole front end.
See The Mathematica Book: Section 2.11.11.
See also: SyntaxQ.