All money changes in value on a day to day basis. What me and tails are saying is that the US Dollar is not doing well in the basis of exchange rates because of the crashing US economy.
For you Americans, you may not see it as things will generally be the same price as it has been for a while. Us Brits can buy many more Dollars for our Pound right now which makes things cheaper to buy in Dollars than it has been for a long time.
It used to be about $1.5 to £1 which meant that if we wanted to buy something which cost us $150 (like TGE), we would be paying £100. NOW, the exchange rate is about $2 to £1 so if we were to buy something that was $150 now, it would cost us £75, saving us some monies!
I hope that explains it...