JPEG IMAGES

Hi Folks

I've noticed on a few occasions that photos on some threads are listed in JPEG file name form. For some reason I cannot access them. When they are blue in color, it says I am not authorized, and when they are black, nothing happens when I click them. Am I doing something wrong? Will my computer not do it? I access this site by PC only.

Thanks for your help
Troy
Yup, an example would be great. Post a link from here.