Most likely, you don't have the pdf plugin installed in Firefox or the plugin just crashed.
In Firefox, go to Tools
--> Add-ons
-->Plugins
and look for Adobe Acrobat PDF plugin in the list. If isn't there, check this to learn how to install it (or re-install it).
Additionally, there is a better way to open PDF files with fancybox other than iframe, so for this html:
<a class="pdf" href="http://www.test.co.u.uk/test.pdf">test.pdf</a>
you can use this script:
$(document).ready(function() {
$(".pdf").click(function() {
$.fancybox({
'width': '70%', // or whatever
'height': '90%',
'autoDimensions': false,
'content': '<embed src="'+this.href+'#nameddest=self&page=1&view=FitH,0&zoom=80,0,0" type="application/pdf" height="99%" width="100%" />',
'onClosed': function() {
$("#fancybox-inner").empty();
}
});
return false;
}); // pdf
}); // ready
I recommended this method for Fancybox v1.3.x since May 2010
Please notice that I set height="99%". If you use HTML5 DCTYPE, it will avoid a double vertical scroll bar. This is because HTML5 initializes margins.
UPDATE.
BTW, integer values go without qoutes so
'width' : '700',
'height' : '700',
should be
'width' : 700,
'height' : 700,
It will save you some headaches,mostly with IE