guys i have to ask something that sounds weird...since the bridge raises when i tune my guitar to D standard...i should Loosen the bridge not tighten :S? And i dont need any extra springs or anything right ?
No, you tighten it. A floyd rose system is all about a balance of tension, the tension of the springs counteracts the tension in the strings and the whole thing lies in it's flat floating position.
If the tension on the strings is increased (going to a higher tuning or using higher gauge strings like Children of COB said) then it pulls the bridge up because there isn't enough tension in the springs to keep the bridge flat.
So, to make the bridge lie flat, in this case, you need to increase the tension of the springs by screwing those screws further into the body. Step by step for doing this:
1. Tune your strings a bit lower than you want them to be (maybe around a half step lower), you don't have to be really specific with this, just lower.
2. Tighten the springs in the back of the guitar until the bridge is flat.
3. Tune your strings again, if the bridge gets pulled up repeat steps 1 to 3.
4. If the bridge is being pulled back into the body once you've reached your desired tuning: then you've tightened the springs too much so just go and loosen the springs.
5. Tune up your guitar.
6. If it's still being pulled back into the body repeat steps 4 - 5 until it's flat.