Sometimes, you'll find an image and post it, and it shows up fine in your post as viewed on your own computer, but no one else can see it. That happens with sites that don't allow hotlinking. Because you went to that site to find the image, the image is in your browser cache, and it displays just fine in your RJ post on your own computer.
The solution to that problem is to always do your image searches with a different browser than the one you post to RJ with. So, if you post to RJ with Firefox, do your image search in Opera, Safari, Internet Explorer, etc. That way, the image is not in the RJ browser's cache, and if the site doesn't allow hotlinking, you'll immediately see that as soon as you preview or submit your post.