Hi Gdk, 


We need some more information on this, are you getting any error?

Are you using a Site in an Iframe and is it Service cooud console?

See the article below, 

Resolution
Modern browsers are forced to defend against a new kind of attack called "Clickjacking" where framing is used by malicious attackers to compromise a browser and potentially steal customer data. More data on this can be found here:

https://www.owasp.org/index.php/Clickjacking

In response, many browsers have implemented a new HTTP header, "X-Frame-Options", and it is gaining in popularity and support for security reasons.  More information on the header can be found here:
http://blog.mozilla.com/security/2010/09/08/x-frame-options/
and here
https://developer.mozilla.org/en/the_x-frame-options_response_header
Salesforce has also implemented its own defenses to clickjacking attacks within the native UI. Due to this, the iFraming of Salesforce, or the iFraming of some external websites may no longer be possible.

As a workaround, customers encountering this problem with a Web tab or custom link can deliver the URL as a custom link with the behavior set to:
Display in new window
Display in existing window without sidebar or header

https://help.salesforce.com/apex/HTViewSolution?urlname=IFRAME-or-Web-Tab-Content-Displays-Blank-Page-1327107637323&language=en_US

Also, 

If you're using Chrome, it will not load cross domain script without approval so click on the Sheild on the address bar and allow unsafe script when you are previewing it

https://success.salesforce.com/answers?id=90630000000hN39AAE


Regards,
Ashish