I've tested your code using chrome 25.0.1364.172m, all appear OK.
Check it: http://jsfiddle.net/rcHMc/
HTML
<div class="widget" id="id_300x250">
CSS
.widget { font-family: arial; height: 250px; width: 300px; border: none; background: url('http://paradigmsearch.co.uk/uploads/widget_background/cached/proportional/300x250/1_512648b566578.png') no-repeat center center;}