You could almost still run PHP scripts from those days. The same basic architecture works you just gotta study the new DB access methods that use prepared statements instead of string concatenation/interpolation.

If you used Perl, mod_perl exists and CGI.pm is available in CPAN. The CGI protocol is as viable as it ever was (though of course there are new and improved alternatives).

There are a bunch of minimal stylesheets out there that get you some mobile compatibility, and no IE 6/early Firefox nightmares, so your code can actually be simpler than ever.