These are useful for some advanced caching behavior, but there are cases where you might find them unnecessary for static files (in particular). Most network analysis tools will call attention to this header value, and while it seems like a trivial amount of bandwidth to send from the server to the client, the real reason for the negative score is more likely related to the behaviors that it causes in the client.
It should be noted that the default value used for the ETag is based upon the ‘inode’ of the file, as such it’s IS problematic in clustered server environments. I’ve shown the correction for this below.
Adding the following to your Apache http.conf file is a start:
# Change ETag to remove the iNode (for multi-server environments)
FileETag MTime Size
#Remove ETag from all static content, this could be done globally without the FilesMatch, but we want better control.
Header unset ETag