<script>
function myFunction() {
// Declare variables
var input, filter, ul, li, a, i;
input = document.getElementById('myInput');
filter = input.value.toUpperCase();
ul = document.getElementById("myUL");
li = ul.getElementsByTagName('li');

// Loop through all list items, and hide those who don't match the search query
for (i = 0; i < li.length; i++) {
    a = li[i].getElementsByTagName("a")[0];
    if (a.innerHTML.toUpperCase().indexOf(filter) > -1) {
        li[i].style.display = "";
    } else {
        li[i].style.display = "none";
    }
}

}
</script>

(via sebsauvage)