If they are vanishing into the floor, I'm guessing you were playing on arrival. It's cheating. Screenshot it with the player's name in focus and send a report to Softnyx.
Or you can record a video with FRAPS---you would have to send the video to Softnyx's alternative mailbox because their regular report system only takes up to 3mb i think--enough for a jpg. FRAPS trial does 30 second clips and the videos are HUGE, get virtual dub to fix that and use the latest divx compressor codec to cut the size down about 8/10ths of the original. FRAPS comes with a tutorial on all that...
MS is abbreviation of milliseconds. Which is how your connection is measured. It's the time in MS it takes for one packet of data to get to that person or back to you. 250 is the absolute highest tolerable.
Lag, refer to above. However the word has lost the original meaning, which is a slang of latency--the delay between two connections.
When someone says "lag" they are trying to pin their failure on their internet connection---nine times out of ten they have a perfectly good connection.
Rank doesn't matter, you have to pretty much rent a weapon for a certain period of time. Don't burn your money on a gun you aren't used to.
SAVE your money.
For new accounts you are automatically rewarded a gun for getting a certain number of kills, which you get a 7 day rental on the guns given. Take time to find out which of these guns you like, but don't bother upgrading. Don't waste money on upgrades unless you know exactly what you're doing, and only do it on 90 day guns.