Why does FB Timeline blur/distort my HD photo when uploaded?

[umer s]

Why does my facebook timeline cover distort/blur my HD photo? I have tried everything! I exported it in HD with Photoshop CS5 851x315 px, 16bit RGB mode.
When I save it to my hard drive, it is crystal clear sharp HD. When uploading to facebook timeline, it makes it blurry. WTH!
Thanks for your answer Charlie - But I'm confused how everyone else has HD pics for their timelines? I haven't come across ANY blurry timelines, APART from mine!? What Am I doing wrong?

If I download 851x315px photos off the net and upload them to fb, they stay HD and work fine. Just not my photoshop exports?

[Charlie Michaels]

Facebook automatically compresses it to make it smaller on their end. No matter how you save it, they'll always make it look like crap.

[Nahum]

Can you post some examples?

Most every JPEG on the web is 8-bits-per-channel. Anything higher is usually not supported. You likely need to convert down in Photoshop so Facebook doesn't do it for you. You may also need to bump down the quality slider—a value of 7 to 9 (by Photoshop's standard) should suffice. Use the "Save for Web" command to compare your original image with the version you intend to upload.