I gave you a bum name. The program is called SQLiteSpy and it's free, here. Just open the file in that, then go to Execute > Vacuum Database which should reclaim some free space.
> haven't seen any reduction in size
That's why you need to use that program, or similar. Don't use the one you edited with Wordpad, just dump that. The file format is sqlite3 and removing entries from them doesn't reduce the file size, it just marks the space as empty. This isn't an issue with Firefox/Opera since they use different formats.
> get to be too big
Just general heavy usage. Things like, each comment/post that gets voted on creates a entry for that author (provided they don't have one already), with a corresponding vote count. If you frequently vote on content then this can add up over time.
> I checked the wiki
It's not mentioned because only a small handful of people have breached the limit so far. That program was the most user-friendly way I could find of shrinking the file back to sub-5MB in size, without having to dig into the file itself. Making manual alterations and just one error can break an entire field of entries.
As ever, keep your original file backed up safely.
Download this. Go to D:\Users\xxxxx\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxx.xxxxx and open places.sqlite with it.
Open the moz_places table and into the query box on the top right put Select * from moz_places where url like "%google.com% , replacing google with the domain of the site you are interested in and run it. Note the ID next to the correct URL.
Next open moz_historyvisits and run, SELECT * FROM "moz_historyvisits" where place_id = 296, replacing 296 with the ID from the previous step. Take note of the visit date, visit this site to convert it to something you can read. Change the timestamp date that it converts to into the one you want and convert back. You will get something like 1306907031, just add 6 0s on to the end for our purposes, to get 1306907031000000.
Now make note of the id of the record that we just changed the visit date for, and run UPDATE "moz_historyvisits" SET visit_date='1306907031000000' WHERE id = 90586 with the correct date substituted in. Then run a SELECT * FROM "moz_historyvisits" where id = 90586 with your correct ID number to ensure it worked. Go ahead and close the db and exit.
That will have changed one history entry. You can likely replace a bunch by doing "where id in (1,2,3,4,5)" instead of specifying one ID at a time. Hopefully you catch on to SQL basics quickly, at this point I don't even care anymore, why am I doing this...Goodnight and enjoy lying to the woman you love!
It's an sqlite3 file. On Windows you can use sqlite browser or sqlite spy, both free. The latter is a bit more user-friendly. Make sure to have Chrome closed when inspecting it.
try sqlitespy - http://www.yunqa.de/delphi/doku.php/products/sqlitespy/index
you can just paste it in and press execute.
Usually I use http://code.google.com/p/phpliteadmin/ <--- that, to manage databases, if you have a web server.