The story began a few weeks ago while I was in koh-samui. My host of choice had a SAN failure and ended up having 4 days of downtime. Unacceptable under any circumstances, so I've started looking at other hosts. I setup a test site on godaddy for one of my clients, but as GoDaddy was also the DNS server, they moved the site as soon as it was setup leaving me with a choice of fixing the DNS back to the existing host, or moving the site in a hurry to godaddy. As my customer wasn't paying for hosting I decided to most the hosting to GoDaddy. Bad move.

The reliability on GoDaddy was perfect, the speed even wasn't bad (not as fast as my locally hosted box, as you'd expect, but not bad).  The issue came because my client was complaining that every facebook share, sometimes the descriptions wouldn't appear in the shared post, and almost always the image was missing.

I went through everything a few times and discovered that if I shrank the featured thumbnail presented to facebook to 100x100, the chance of it appearing increased to about 50%, but was still unacceptable. The links were fine, and my browser was able to see the image_src and pick the image up.

I finally gave up and moved the site back to the old host and immediately it started working correctly. Strange. Lesson learnt - cheap hosting just isn't worth it.

They all use the same template so I thought surely the html would be very similar... and it was. I ran the pages through the w3c validator, and made a bunch of unecessary changes to do with short-tags and pulled my hair out some more.

A few more coffees and some tweeting and googling brought to my attention that the error "The message could not be posted to this Wall." could be due to facebook blocking that url due to abuse... maybe one of our competitors complained to upset our social strategy? no - then all of the urls would be broken (only lost an hour here )

I went back to the HTML, removed anything fancy and it still didn't work. I decided not to let this get the better of me, and I went through the html line by line looking for anything out of the ordinary... and there it was.

Canonical link was missing a slash. <link rel="canonical" href="https:/somedomain.com" />. Now this was set by our e-commerce system, not by the template or development, and none of that has changed for a really long time, meaning that something at facebooks end has tightened up the validation. Anyway, not pointing fingers, commented it out and Posts are now sharing as expected. ugh.