raymondcc - 3:01 pm on May 4, 2013 (gmt 0)
ted is right.
Errors generated by webmaster can hurt their website but not if they are generated externally (meaning other website linked wrongly to your pages)
I am one of them who "shot themselves in the foot". A plugin conflict generated over a hundred thousand not found errors in Google Webmaster Tools. Traffic started to dip and I am still waiting for recovery.