Hello,
If you are referring to the game Special Force Online, it rather depends on where you live it seems, the game is intended for the Philippines only, after some discussions on their forums i was able to find out that they only allow people from the Philippines and a few other selected area's to play the game online because their servers can't handle any more traffic than that generates, they just aren't geared up for an international market and they will almost certainly block IP addresses from other countries.
Assuming that you are fortunate enough to be able to connect at all, the best place to get more information about the game would be
http://www.mygame.ph but you may get an error on the web page if you are in a blocked country/region.
If you are referring to Battlefield 2 : Special Forces, there isn't a downloadable version of the game that i am aware of, and certainly not one that would work online, the game is very cheap to buy now and i would suggest you pick yourself up a copy at your local software store.
If you are referring to Americas Army : Special Forces, try looking at
http://www.americasarmy.com where you can download a free copy of the game. The game is distributed freely and you are able to download and play the game online.
Regards,
[ESF]-Predator