[tsigel]

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.js"></script>
Ширина <input id="width" type="text" /><br>
Высота <input id="height" type="text" />

<script>
$(window).resize(function() {
  initResize();
});

function initResize() {
  $('#width').val($(window).width());
  $('#height').val($(window).height());
}
</script>