I had difficulty getting a new picture into one of my standard picture of the day pages. No matter how carefully I copied the HTML code from flickr, I got the alternate message indicating the picture couldn't be found.
I plugged in the HTML for an old picture, and the page worked fine. I plugged in the HTML for the new picture, and the picture couldn't be found. I used the URLs to look at the pictures in another browser; they were displayed fine.
I went to flickr's message board and picked a couple of topics that seemed relevant. I waded through message after message reporting having difficulties with flickr. And message after message complaining about others' posts. And message after message complaining about complaining about others.
Finally, on a second topic I found a message from flickr staff that my browser's cache may have lost the picture but didn't know it. I diddled around with the browser a bit, including closing it at least once. I was very frustrated and so I just floundered around without noting what I did. However, the important point is that the picture now appears in my web page (http://www.cpinternet.com/~mdmagree/picture_of_the_day.html today and tomorrow or soon http://www.cpinternet.com/~mdmagree/picture_2007-09-07.html).
Most of the time I'm not so lucky to find a relevant answer.