Why do my Pokemon's attacks always miss sometimes?

I'm playing Pokemon Emerald and my character ingame name is Brendan. I chose Mudkip and when he only knows Tackle, the game makes a mistake saying that his attack missed. This makes me mad so please help me. Why does his attack always miss unless it's Mud Slap or Water Gun? Please help or do I need a better strategy to help start out the game? I haven't played Pokemon in a longer time now than expected.