Hello and welcome to MacRumors. It appears English isn't your first language so I'll try to keep this simple.
In order for anyone to help you, you will need to provide as much information as possible. What you have provided above is simply not enough for anyone to help you.
Here is a list of some questions you should answer so we can try to assist you:
Has this happened more than once? If not, it's nothing to worry about.
What game were you running?
Have you contacted the developer of the game to explain the error? The developer is much more likely to be able to help you with this issue.
What browser were you running?
What OS X version were you running?
What Mac were you running it on?
Again, provide as much detail as you can or there is no chance you will receive any assistance.
i think i just need to re install java but i dont know how on a mac all the internet says when i google it is to go to software update. i basically just need a working java download