Hey Enrique!
Here are your options to build the game's world:
- Module assembly (pre-made rooms mixed and matched randomly)
- Terrain generation (multiple options, procedural)
- Handmade content (used to create both entire maps and map modules)
- Modify by hand generated maps (create entire map with terrain generation and module assembly and then improve it by hand)
Let me know if you have any questions! :)
For what regards publishing for the web, I can't make promises about it yet but it should be possible to convert your game into javascript!