Pokémon Ruby Version, Sapphire Version, and Emerald Version - Stacking Effects
Generally, moves with the same effect code don’t stack with each other. For example, the moves Block, Mean Look, and Spider Web share the same effect. Once any of these moves is used, they will fail against the same target until the effect is removed. Multi-turn attacks such as Wrap and Whirlpool also share the same effect for a given target and don’t stack with the use of different kinds of multi-turn attacks.
Effects of the same move also don’t stack with each other unless noted otherwise. For example, Ingrain can’t be used multiple times on the same Pokémon. However, Stockpile and Spikes can be used multiple times for a bigger effect (Spikes says "Can be used up to three times", and Stockpile raises the user’s Stockpile count up to a maximum of 3).