Javascript e.keyCode doesn't catch Backspace/Del in IE

I'm trying to catch the pressing event of Backspace and Delete keys using javascript/jQuery with this kind of code.

$("textarea[name=txt]").keypress(function(e){
    var keycode =  e.keyCode ? e.keyCode : e.which;

    if(keycode == 8){ // backspace
        // do somethiing
        alert(keycode);
    }

    if(keycode == 46){ // delete
        // do somethiing
        alert(keycode);
    } 

});

These lines of code works perfectly in Firefox (3.6.12). That means the alert is popped up when Backspace or Delete is pressed. But this is not working in Internet Explorer (8)

Can anyone suggest me a different way to catch these key press events in Internet Explorer?