Fred, the image looks overall just a tad underexposed the mid tones look a little on the heavy side and there is something going on with the land area, have you blurred it in some way, it doesn't look natural to me. The puffin in flight appears to have been well fouced and captured, the underwings could benefit from being a tad brighter.
Fred that was a heck of a crop, the colours have also changed. May be worthwhile checking your technique in Save for Web. I don't wish to teach you to suck eggs but if you are unsure there is plenty of help available.
I never mind getting advice, trying to learn everything by doing, is a long and hard process. You have a good point, right now I don't save for web, I just edit the original and let Lightroom process for web during the export, which I set the appropriate long side dimension.