Found the following HTML validation problems:
a0_b_control.html:19:1 (a0_b_control.Rd:7): Warning: <h2> attribute "id" has invalid value "ZMQ Control Environment"
a0_b_pbd_opt.html:19:1 (a0_b_pbd_opt.Rd:6): Warning: <h2> attribute "id" has invalid value "Set Control Functions"
a0_c_options.html:19:1 (a0_c_options.Rd:8): Warning: <h2> attribute "id" has invalid value "Initial Control Functions"
a0_d_context.html:19:1 (a0_d_context.Rd:7): Warning: <h2> attribute "id" has invalid value "Context Functions"
a1_socket.html:19:1 (a1_socket.Rd:12): Warning: <h2> attribute "id" has invalid value "Socket Functions"
a2_message.html:19:1 (a2_message.Rd:7): Warning: <h2> attribute "id" has invalid value "Message Function"
b0_sendrecv.html:19:1 (b0_sendrecv.Rd:7): Warning: <h2> attribute "id" has invalid value "Send Receive Functions"
b1_sendrecvfile.html:19:1 (b1_sendrecvfile.Rd:7): Warning: <h2> attribute "id" has invalid value "File Transfer Functions"
b2_sendrecv_multipart.html:19:1 (b2_sendrecv_multipart.Rd:7): Warning: <h2> attribute "id" has invalid value "Send Receive Multiple Raw Buffers"
b2_sendrecvdir.html:19:1 (b2_sendrecvdir.Rd:7): Warning: <h2> attribute "id" has invalid value "Transfer Functions for Files or Directories"
b3_poll.html:19:1 (b3_poll.Rd:9): Warning: <h2> attribute "id" has invalid value "Poll Functions"
xx_czmq_wrapper.html:19:1 (xx_czmq_wrapper.Rd:5): Warning: <h2> attribute "id" has invalid value "C-like Wrapper Functions for ZeroMQ"
xx_rzmq_wrapper.html:19:1 (xx_rzmq_wrapper.Rd:11): Warning: <h2> attribute "id" has invalid value "Wrapper Functions for rzmq"
xx_utility.html:19:1 (xx_utility.Rd:7): Warning: <h2> attribute "id" has invalid value "Utility Functions"
zz_overwrite_shpkg.html:19:1 (zz_overwrite_shpkg.Rd:6): Warning: <h2> attribute "id" has invalid value "Overwrite shpkg"
zz_zmq_control.html:19:1 (zz_zmq_control.Rd:10): Warning: <h2> attribute "id" has invalid value "ZMQ Control Functions"
zz_zmq_flags.html:19:1 (zz_zmq_flags.Rd:9): Warning: <h2> attribute "id" has invalid value "ZMQ Flags"