If you double-click anywhere on a word of text in any application on Windows, it will highlight that word and any following whitespace characters upto the beginning of the next word. Supposedly, Mac behaves the same way too.
The reason for this behaviour seems to be to aid in copy-paste of a word inside a document. It also helps if one wants to delete a word, since the following whitespace is also nicely removed.
However, I find this behaviour quite anachronistic and irritating. Especially when I am editing text on Firefox and want to apply formatting on the highlighted word either in rich text mode or HTML mode.
Thankfully, there is an obscure feature hidden in Firefox to make it highlight only the word on a double-click and ignore the following whitespace. Open
about:config and set
layout.word_select.eat_space_to_next_word to false.
Tried with: Firefox 4