What do the percentages do in this CSS snippet?

Question

#header div {
0% { text-shadow: 0px -2px 20px #E88E00; }
25% { text-shadow: 0px 0px 25px #E44E00; }
50% { text-shadow: 0px -2px 30px #E00E00; }
75% { text-shadow: 0px 0px 25px #E44E00; }
100% { text-shadow: 0px -2px 20px #E88E00; }
}

Answer 1

This isn't a valid css code...
Maybe ( surely :P ) you've found something like:

#header div {
animation: /* some parameters */;
}
@keyframes animName {
0% { text-shadow: 0px -2px 20px #E88E00; }
25% { text-shadow: 0px 0px 25px #E44E00; }
50% { text-shadow: 0px -2px 30px #E00E00; }
75% { text-shadow: 0px 0px 25px #E44E00; }
100% { text-shadow: 0px -2px 20px #E88E00; }
}

... and percentage set when occurs the key change of parameter, on the duration timeline of the animation ^^

Answer 2

are you sure the code is valid CSS code? correct the code first.