The ProQ web server for protein model quality assessment is no longer available. Its successors are:
ProQ3 — web server for model quality assessment (ProQ3, ProQ3D).
ProQ4 — deep-learning based quality estimation, available as a program to install and run locally.
If you used ProQ, please cite: Björn Wallner and Arne Elofsson (2003). Can correct protein models be identified? Protein Science 12(5):1073–1086.