What does the "?" mean in this?

[Al Smith]

Hi,
In the code below, what does the question mark do in the lines var keyCode... and var filter...?

var isNN = (navigator.appName.indexOf("Netscape")!=-1);

function autoTab(input,len, e) {
   var keyCode = (isNN) ? e.which : e.keyCode; 
   var filter = (isNN) ? [0,8,9] : [0,8,9,16,17,18,37,38,39,40,46];
   if(input.value.length >= len && !containsElement(filter,keyCode)) {
   input.value = input.value.slice(0, len);
   input.form[(getIndex(input)+1) % input.form.length].focus();
   }

Thanks,
Al.