UniProt is moving web pages and services from HTTP to HTTPS:
We will support separate HTTP and HTTPS services until release 2018_06 (June 20, 2018). From this date, the HTTP traffic will be automatically redirected to HTTPS. We intend to maintain these redirects indefinitely, but it is to your advantage to update your applications to use HTTPS as soon as possible, both for performance and security reasons.
Please refer to this announcement: https://www.uniprot.org/help/https_change