The index to the HDF5 File Format Specification on the right side of the page, the links take you to the correct section.

But you cant cut and paste the link, for example into this document, so that someone can click on the link and get to that section.

For example https://support.hdfgroup.org/documentation/hdf5/latest/_f_m_t3.html#subsubsec_fmt3_dataobject_hdr_msg_layout takes you to the top of the document, instead of to the subsection IV.A.2.i. The Data Layout Message.

This is a pretty important functionality. Hopefully its an easy fix.