How much page-specific Javascript / CSS are we talking about, and how much traffic does your site get? I'd personally put global Javascript / CSS in secondary files (as you suggested), and template the page-specific stuff directly into each page. This eliminates the delay of waiting for external files to load, and keeps bandwidth consumption relatively low.

If you're still having server speed / bandwidth problems, get a better hoster.

EDIT: While there might be only three or four generic text sizes (and spacings, and styles, and so on) across a site, each specific page might need to make use of several more, and there's no point putting piles of extra CSS in your primary file. Hopefully this is what he means. If on the other hand he just wants to feed different CSS to different browsers, it would probably be better to make a .css file for each of these browsers and dynamically write just the name of the file.