Das war etwas schlampig. Hier noch einmal ...
var li_elements = document.getElementById("main").getElementsByTagName("li");
for(var i = 0; i < li_elements.length; i++) {
var li_element = li_elements[i];
if(li_element.className == "hover") {
li_element.onclick = goto;
}
}
function goto() {
var link = this.getElementsByTagName("a");
var adress = link[0].href;
window.location.href = adress;
}