3 way switch

i installed a 3 way switch and when i flip the switch1 to off im not able to turn on switch2 until switch1 is turned on ........ when i turn on switch2 and off im not able to turn on switch1 ...... vice versa whats wrong

 

The incoming hot wire should go to the common screw on 1 switch(the black screw) and the black that goes to the light fixture should be on the common of the other switch.
Go Here to learn more about three way switches and wiring diagrams.

 

You've misidentified the common. If you only touched one switch, then that's the one. Fix it by trial and error. There are three wires and three screws. Rotate them around. You'll find the answer in three tries or less.

 

Am assuming you replaced an existing 3-way switch with a new 3-way switch. If that's the case, you probably just reversed a couple of wires. One of the terminals on the switch is a different color (usually copper- or reddish-colored). That terminal should be connected to the "hot" if the switch is on the electrical source side of the circuit. It should be connected to the load (light fixture or outlet) if it's on the load side of the circuit.

Ideally, when replacing a 3-way switch, you tag/mark the wire removed from the different colored terminal and put that wire on the corresponding terminal of the new switch. Doesn't matter if you reverse the other two.

To correct the problem using trial and error method, you can reverse two wires at a time on the switch until you happen upon the correct configuration (remove power to switch before removing and connecting wires).

If you installed two new switches, hopefully you can identify the wire routes and then just follow the guide in the first paragraph to connect the correct wire to the different colored terminal. The remaining two switched "hot" wires going between the two switches can be connected to either of the silver (or brass?)terminals. And, of course, ground to ground.

Hope this helps...