var sections = document.getElementById("content").children;
var active = 0;

function changePage(id)
{
    var next = parseInt(id);
    if (active != next)
    {

        sections[active].style.opacity = "0";
        setTimeout(function()
        {
            sections[active].style.display = "none";
            sections[next].style.display = "block";
        }, 250);

        setTimeout(function()
        {
            sections[next].style.opacity = "1";
            active = next;
        },500);
    }
}