Huge amount of empty space, and YSlow

Ever look at your source code? I've noticed for a while now that there is a tremendous amount of empty white space in my Wordpress pages. I don't know if it's the theme or just built in to Wordpress, but it bothers me. I've been doing HTML since Tim Berners-Lee was a pup, and I remember always hearing that it wasn't "proper" coding to leave lots of white space, because the browser actually has to "read" it as it renders the page. Makes sense, but I'm not sure if it matters anymore. That was in the days of dial-up (remember that, boys and girls?), and maybe it's not a significant problem now.

But I did look at my Google Analytics visitor data, and there are still some poor souls on dial-up accessing my site. Even DSL can be pretty slow, so I hate to make the site load any slower than necessary. And the code looks untidy to me. All the CSS at the top also bothers me, but I"m not sure I should remove that and call it separately

I also ran YSlow, and was told I'm running 11 external javascripts which should be combined. I don't know how to do that with Wordpress except run a plugin.

It also says I have 47 separate components that are not on CDN, whatever that is...

There are other areas where I got F or D grades, but they seem to be part of Wordpress, nothing I'm doing wrong.