[Ivan858]

function nextBtn(btn) {
    var n = btn.id;
    if(btn.id=="b1") n = "b2";
    else
			n = "b1";
    return document.getElementById(n);
}
function btnclick() {
    activebtn.style.backgroundColor = disactiveclr;
	activebtn.style.fontFamily = disactivefont;
	activebtn.style.fontSize = disactivesize;
    activebtn.onclick = null;
    activebtn = nextBtn(activebtn);
    activebtn.style.backgroundColor = activeclr;
    activebtn.onclick = btnclick;
}
var disactivesize = "20px";
var disactivefont = "Georgia";
var disactiveclr = "white";
var activeclr = "red";
var activebtn = null;
function ld(){
    (activebtn = document.getElementById("b1")).onclick=btnclick;
}

Только сильно не бейте