flights from country to country

True: They are less expensive if purchased online in advance (the more in advance the cheaper it gets - usually). Not true: Online in those countries. You can book them online from back home as well.

Buy here before you leave. Discount airlines in Europe will give you the best deals the farther out you purchase your tickets. Check whichbudget.com for city pairings to find out the discount airlines that fly those routes. You can compare them, then, with the "big boys" like Air France, BA, BMI, etc, who may offer similar fares, but better schedules, on those runs where they're facing discount airline combination. In all cases, check refund and change policies, and luggage weight restrictions and charges.

When I looked up my Croatia Airlines flight in Expedia and Travelocity..etc.etc..It was 4x the amount than when I went to Croatia Airlines website directly!

Some websites have good deals, but what I noticed is that before tax the price looks fine , after that it migt double.You have to compare.
Here are some European web sites you might want to take a look:
myair.com
wizzair.com blueair.com skyeurope.com

So far I have not found a good price for what I looked. I looked at a fare from Prague to Bucharest, Romania in March and it was almost $500.This is a lot.
I paid $640 from Cleveland to Bucharest.

Bea...unfortunately, there are no discount airlines flying Prague-Bucharest, which is why the price remains so high. But for common routes that Nancy is looking at, like Manchester-Paris, there are lots of combinations available. A service like whichbudget.com will list each of the airlines you mention if they're flying those city pairs, meaning less "clicking around" to find flights available!:)

If you book early you can get some really good deals. I booked Paris Orly to Munich for 1 Euro base fare on Air Berlin. Also booked Munich to Rome (FCO) for 9 Euro base fare on Air Condor.