set_splash_height.js

// Without jQuery:

var setSplashHeight = function () {
    document.getElementById("splash").style.height = "innerHeight" in window ? window.innerHeight : document.documentElement.offsetHeight; 
}
setSplashHeight();
window.onresize = setSplashHeight();

// With jQuery:
var jSetSplashHeight = function () {
    $("#splash").height($(window).height());
}
$(window).bind('onresize', jSetSplashHeight);
jSetSplashHeight();