This is a specification table for line breaking.

The values of IE7 and Opera9: 'A' means that the line is breakable After the character, and 'B' means Before. 'BA' means Before and After.

(C) which is the tail of the IE7 and the Opera9 means Character. (N) means Numeric. This means that they are around the character at testing. E.g., "a$a" is a testcase for (C), "0$0" is a testcase for (N).

Gecko is not breaking the lines on most western language context. But for file paths, URLs and very long word which is connected hyphens, some characters might be breakable. They are 'breakable' in the table. However, they are not always breakable, they depend on the context in the word.