w3c markup validator ampersand (&) error

Есть ли способ обхода ошибки проверки w3c для и , присутствующих в URL-адресах или другом месте в разметке HTML?
It says:

& did not start a character reference. (& probably should have been escaped as &.)

The ampersand in my case is a part of a url for gravatar thumbnail. This is the problematic part of a url:

c91588793296e2?s=50&d=http%3A%2F%.