Last-Modified, If-Modified-Since, Expires, use it or not?
 

As the title suggests, better use them or better not?

Last-Modified
If-Modified-Since
Expires

It applies to all? Or maybe some it is better to use them and others better not?

Thanks for the answers

What are you talking about?

The answer is Yes.

Except when it is No.

Or Maybe it is Maybe.

.

I'm only using Cache-Control on my sites. seems like pretty much every modern browser supports it.

And in htaccess?