You can't. Not to HTML. HTML is a fixed web markup language.
(But, it would be the other way if you could - you would connect the HTML to the database...)
However, you CAN use a web programming language like PHP, ASP or ASP.Net to connect to a PostgreSQL database. You connect the same way you would to any other database, just use a PostgreSQL specific connection string.
I'm not a web programmer, though, so I'll leave the specifics of how to do so to others.
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