Are you trying to add an image to a popup in the "popup media" section of the popup configuration panel?
What is the URL you are providing to the image? It has to be an actual URL to a PNG, JPG, etc. not a link to a web page. Here's a link to one of my images in Picasa Web Albums. Try using this one; it works for me.
Also, in Picasa, when you upload images to an album, you probably need to make sure it's not marked as private. I didn't try that specifically, but I'm guessing it might not work in this case.
Dear Mike, Thank you for your speedy reply. I am trying to link photos from my Picasa album called "Community Atlas to ArcExplorer Online. I created a feature in ArcExplorer and want to add a picture to the "Edit Popup" window in. Because I created the feature, there is no configure pop-up option. (See screen shot.)
I can see that there is no jpg extension to the link in Picasa and if this is the problem; how do I create an extension? (See screen shot) Yours, Margaret
It looks like you're running on a Mac, so hopefully this info will be the same.
In Safari on the PC, if I right-click an image, I see a "Copy Image Address" option which copies the URL to the actual image. This is the URL to just the image. There may be other ways a browser can return the url of an image, but this is one easy way.
You probably will want to get the image url when looking at this page, rather than your album page which shows thumbnails.