ATTENTION! Word Count Plus is not currently compatible with Firefox 3.6. I am working on a new version now. In the meantime, if you force compatibility (like with Nightly Tester Tools) you will be able to count words, but switching between windows will result in buggy behaviour.
Word Count Plus sits unobtrusively in the status bar of the active window, where it shows you the number of currently selected words. You can choose to add that number to a counter, in which case you will also see a running total.
New versions of this extension are first made available at mozdev.org: http://wordcountplus.mozdev.org/
To try out a beta release that includes keyboard shortcuts, download version 1.3.0: http://wordcountplus.mozdev.org/betarelease.html
If you have trouble using Word Count Plus, please feel free to leave a review detailing the problem, but be aware that I may need to contact you directly for more information. If your email address is not listed in your account profile, please use the mailing list to submit a support request: http://www.mozdev.org/mailman/listinfo/wordcountplus
To use, select some text on the page, then right click and choose Count Words from the menu. The word count will show up in the status bar. You can also choose Add and Count Words to keep a cumulative word count, so you don't need to open a calculator application to figure out the total word count across multiple text selections.
Another way to trigger counting is to click in the status bar area:
1. Left-Click to Count Words.
2. Shift-Left-Click to Add and Count Words.
3. Middle-Click or Alt-Left-Click to reset the counts to zero.
To access the full array of commands, right click in the status bar area to pull up the menu.
1. The Auto Copy Counts option will copy the count to the clipboard immediately after a count is triggered.
2. The Auto Text Deselect option will remove the selection from the text immediately after a count is triggered.
3. The Options dialog allows you to provide a custom thousands separator and a custom copy format.
1. Can count selected words in a focused textarea or text input box. Notice that the box must have the focus.
2. Has primitive character counting abilities. The character count doesn't show up in the status bar and you can't copy it to the clipboard or do anything with it really, but if you want to see the selected and total character counts, you can hover in the status bar panel and they show up in the tool tip text.
If you're running Windows XP Home and find that Word Count Plus is refusing to install, make sure you've installed SP2 and that should clear up the problem.