Reference:
'fileExt': '*.jpg;*.jpeg;*.gif;*.png',
For Size limit. You can also change the size.
'sizeLimit': (600 * 1024), //600 KB
Complete Script
<script type = "text/javascript">
$(window).load(
function () {
$("#<%=FileUpload1.ClientID %>").fileUpload({
'uploader': 'scripts/uploader.swf',
'cancelImg': 'images/cancel.png',
'buttonText': 'Browse Files',
'script': 'Upload.ashx',
'folder': 'uploads',
'fileDesc': 'Image Files',
'fileExt': '*.jpg;*.jpeg;*.gif;*.png',
'multi': true,
'auto': true,
'sizeLimit': (600 * 1024), //600 KB
onError: function (a, b, c, d) {
if (d.type === "File Size") {
// Display error message in span
$("#err").html('File: ' + c.name + ' Maximum ' + d.type + ' Limit: ' + Math.round(d.sizeLimit / 1024) + 'KB');
}
}
});
}
);
</script>