how can i remove ytimg.com

Assuming that is adware and you are getting popup and other problems with Safari try:

How to install (Really remove) adware
https://discussions.apple.com/docs/DOC-7471

Stop pop-up ads and adware in Safari
https://support.apple.com/en-us/HT203987
Adware Removal Guide : Identification
http://www.thesafemac.com/arg-identification/
Next if necessary:
Malwarebytes Anti-Malware for Mac
https://www.malwarebytes.org/antimalware/mac/?gclid=CjwKEAjw8qetBRCj6vKH8IC_kwoS JADGQ8dSXC2m8LzIJ_6AwtK7xznQOvkb7qN3FBqVS_jjw8JcdhoCCqDw_wcB
MB for Lion:
https://data-cdn.mbamupdates.com/web/MBAM-Mac-1.0.2.8.dmg

In Reference, ytimg is not a virus, its Youtube's Image service url.

See full document below- https://support.mozilla.org/en-US/questions/1086445