<link rel="image_src" href="http://example.com/logo.png" />

Just put that tag in the head portion of your HTML, and the image specified (in this case “logo.png”) will be the new default (and only) choice for Facebook sharing. There are a few things that you should know though. First, Facebook caches these images, so you may not see the immediate change. I’m not sure exactly how long the cache is, but I saw changes in under 24 hours on a site I was working on. The other really big thing to know about is that Facebook has specific rules for the image:

The thumbnail’s width or height must be at least 50 pixels, and cannot exceed 130×110 pixels. The ratio of both height divided by width and width divided by height (w / h, h / w) cannot exceed 3.0. For example, an image of 126×39 pixels will not be displayed, as the ratio of width divided by height is greater than 3.0 (126 / 39 = 3.23). Images will be resized proportionally.

That’s per the developer wiki. Although some other sites also make use of the tag and specified image, your image must meet these requirements for it to work with Facebook sharing. If your image does not meet these requirements, it will not show up at all, and no other options will show up either. People will not be able to select any thumbnail when sharing your site.

It’s also worth noting that Facebook makes use of the traditional meta tags (title and description), so you should be sure to include those on your pages. I know many people have gotten out of the habit of adding them in because they were most commonly used with search indexing, but most search engines use context from your actual content instead of those tags.

I am working on integrating Delicious within an existing application, so I decided to create a test account. That’s when I first ran into issues with the Yahoo integration because I was required to go through the ridiculous Yahoo registration process instead of the previous Delicious sign up. After trying a million different usernames and getting the initial CAPTCHA wrong, I had an account and my testing could begin.

My script was not successfully adding a bookmark, so I tested it directly in the browser and realized I couldn’t log in. I tried the username and the username@yahoo.com, but neither worked. I was able to sign in via Yahoo, so I know I was using the right password. I tried my old Delicious account from 2006 that I never associated with Yahoo, and it worked fine.

I ran into a thread of people having the same issue, and then I stumbled across a Yahoo developer forum thread that clued me in on the comments that appeared in the blog post about the integration. A comment from “Chris” revealed a bit more:

Apologies. It looks like our help pages didn’t get updated.
For accounts created with a yahoo ID, you can use pretty much the same api’s except:
1) You need to use OAuth, as per http://developer.yahoo.com/oauth/, with Delicious as a scope
2) use /v2 as the path rather than /v1
3) You can use http rather than https

The problem with this (well, one problem with this) is that it requires two different ways of handling user authentication for the same service. There is currently no indication of best practices (e.g., should the user self-identify as being a standard Delicious account holder vs. a Yahoo account user or do we check submitted IDs to determine which method should be used to access the API?). There is also no indication of whether developers should expect to support two types of IDs forever.

The biggest reason this is so frustrating is because an API change so significant should be planned months in advance with plenty of forewarning for all developers. Instead, the effect to the API isn’t even mentioned in announcement blog post nor is anything posted in the API docs. Disappointed wouldn’t accurately describe how I felt when I stumbled into these issues….