Rotating Background Color CSS

[tah]

I'd like to do this to the top section of my site. How would I go about incorporating the code on the page linked below? Can't link page...not enough posts so I've attached the code.....

FWIW: I had cade from another source (pretty much the same function) and I pasted it into the CSS frame for the section but it caused the entire site's background to color shift.

html,
body {
height: 100%;
}

.mydiv {
width:100%;
height:100%;
color:black;
font-weight:bold;
animation: myanimation 10s infinite;
}

@keyframes myanimation {
0% {background-color: red;}
25%{background-color:yellow;}
50%{background-color:green;}
75%{background-color:brown;}
100% {background-color: red;}
}