you need to modify css directly since fancybox is not part of jquery.
$("#fancybox").css({'width': '500px', 'height': '500px'});
there is such a method or something like that,
jQuery(document).ready(function() {
$.fancybox(
{
'autoDimensions' : false,
'width' : 350,
'height' : 'auto',
'transitionIn' : 'none',
'transitionOut' : 'none'
}
);
});
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