https://validator.w3.org/nu/?doc=http%3A%2F%2Fopac.niscair.res.in%2F
Right now, the validator is returning a 500 error for that OPAC, and a direct attempt is timing out (504 from a CentOS server) so I can't see the results.
Perhaps because we're all piling on that OPAC to look for errors. I think the point of the conversation isn't to criticize that particular OPAC (they didn't volunteer) but to recommend that as people approach the job of customizing their OPAC they keep validation in mind as a testing tool.
What are these "2 info and the first error message"? Our Koha instance does not have any errors, warnings, info (due perhaps to the evolution of !doctype from XHTML to HTML[5]):
<https://validator.w3.org/check?uri=http%3A%2F%2Fopac.navalmarinearchive.com>
If you're genuinely asking a question, rather than snarking about upgrades: The HTML5 specification no longer considers "unapi-server" an acceptable value for the attribute "rel" on <link> elements. This has no effect on the functionality of the OPAC. -- Owen -- Web Developer Athens County Public Libraries http://www.myacpl.org