In case your website is HTTPS enabled, is loading correctly on the popular browsers, but on Safari it's returning "Safari could not open the page because the server stopped responding", please unset or ask your hosting provider or web developer to unset "Upgrade" http header.

Usually you can disable it by adding this line in your .htaccess file:

    <ifModule mod_headers.c>
        Header unset Upgrade

If it still doesn't work, please open a General Support Request.