Package check result: NOTE

Check: CRAN incoming feasibility, Result: NOTE
  Maintainer: ‘Barry Grant <bjgrant@ucsd.edu>’
  
  Found the following (possibly) invalid URLs:
    URL: https://webclu.bio.wzw.tum.de/stride/install.html
      From: man/dssp.Rd
      Status: Error
      Message: server verification failed: certificate has expired. (CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none)