Where Is Birth Island In Pokemon Emerald?

First you go to professor birch and talk to him once you have caught 100 pokemon and he will tell you that its looking more like a pokedex now.After that he will tell you to go to lilycove city and go into the department store and there will be an old man who'll give you a ticket and once you have it mix records with your friends to give it to them.once you get to the island you have to figure out a code and you'll find deoxys. The code is just to walk on all the triangles

sources:wikianswers