sbm12

In looking at my Picassa Web album I have the option when looking at an individual photo to "link to this photo" in the right side toolbar. I end up with a link that looks like this when I click on that option:
There are a couple important pieces in there that are useful. First, you don't actually want the "A HREF=" tag, so that should be deleted, as should the /a tag that closes it (the stuff in red), leaving you with this:
The other important bit is the s400 that I bolded & made green above. That part of the URL controls the size that the image is rendered in. The acceptable values are s144, s288, s400, s640, s720 and s800.

Using the above process I end up with the following URL for your picture of crossing the Straits of Gibraltar:
Putting that in the image tags in this forum renders this:


The other way to get the correct URL for the image would be to right-click on it and choose properties. In the "Address (URL)" field you'll have something that looks like this:
That is basically the same URL, but with the size information at the end rather than at the beginning. If you choose that format you still have to use a "valid" value for the image size, which is the same set of numbers that I listed above (and there may be others but those are the ones I know work).

Image courtesy of AC110, from the View from Your Hotel Room thread.