Why is my timeline cover photo so blurry?

[Jay]

i created my own cover photo in photoshop and used a canvas size 850x315 which is the exact size of a regular cover photo according to FB.in photoshop it looks razor sharp but as soon as i upload it it looks all blurry and fuzzy. help please?

[Nick]

Don't confuse what you see in Photoshop for what you saved.... if you saved it as a jpg, the one you worked on (the psd) won't change to reflect what it looks like after you saved it in a different format.

Save it using "file > save for web & devices..." instead of just "save as...".
1. You get a preview of the final result before actually saving it,
2. You have more setting options,
3. You can compare up to 4 different formats (and/or settings) using the 4-up view in the save for web window. I usually keep the first one as the .psd to compare the other 3 versions with it.