I implemented the code above. The FB buttons appear and link to Facebook correctly, but I'm getting the following message:
404 - PAGE NOT FOUND
404 means the file is not found. If you have already uploaded the file then the name may be misspelled or it is in a different folder.
Seems to be with the image link. On my site, I hovered over my logo and copy-pasted the image URL of my logo png file into the script above. Not sure why I'm getting this message.