403 Forbidden for many assets

[muety]

On almost any website, I'm getting several 403 errors for different types of assets, pages, etc. The response body says the following:

Error code 403.

Message: Access denied.

Error code explanation: 403 = Request forbidden -- authorization will not help. 

I also see that requests are made using HTTP/1.0. Might that be an issue, because the target webservers don't support version 1 anymore or so?