Use all % or all pixels(find screen pixel height in js)
<html style="margin:0px 0px 0px 0px;padding:0px 0px 0px 0px;">
<body style="height:100%;width:100%;">
<div style="height:3%;background-color:red;"></div>
<div style="background-color:black; height:94%;"></div>
<div style="height:3%;background-color:blue;"></div>
</body>
</html>
Other perfect answer derived from above answer
<html >
<style type="text/css">
* {
margin: 0;
}
html, body {
height: 100%;
}
.wrapper {
min-height: 100%;
height: auto !important;
height: 100%;
margin: 0 auto -20px;
}
.footer, .push {
height: 20px;
}
.header {
height: 20px;
}
</style>
<body >
<div class="wrapper" style="background-color:#ffcc00">
<div class="header" style="background-color:#cccccc"></div>
<div class="push"></div>
</div>
<div class="footer" style="background-color:#cccccc"></div>
</body>
</html>