There could be a case when flickr website may be is blocked your office, and you are not able to access some images on flickr as the the URL structure you are using might be blocked by your administrator.
Normally the URL structure of any photo on flickr is like one given below
Default Flickr URL:
However you can change the structure of the above URL to access the picture if the above URL structure is blocked at your office location.
Modified Flickr URL:
This way you can access any blocked image at flickr if it is blocked at your place, just by changing the URL a little bit.
[ Source: My Digital Life ]