What I have the most trouble with are the offsite photo hosting sites. When redirected to another site sometimes advertisements and other crud load first, before the photos load. The ads often require loading an ActiveX control to drive the cute little animations about how to find your dream sweetie (for example). If you are getting the prompt (yellowish strip) it means your browser is either trying to block something that you have to manually override (depending on your security settings) or doesn't know what to do with the URL. If you click the strip and say ok, it still may take some time for stuff to load. Right click on the x box of a photo you can't see and choose properties. That will give you the URL (uniform resource locator), which you can copy and paste into a new tab's address bar. If it still doesn't work, I just say the heck with it. I resent those sites that insert ads and other junk and make a note not to ever use them.
If you can post the URLs of a couple that aren't working, I may be able to tell you more specifically what the problem is.