call stylesheet in a header file?

I’m not sure how this is done in 1.5, but in 1.22 is it possible to make the call to the css stylesheet in another header file or do I have to have it located within the head section of my index? Also since I have a nav bar on my page, is there another way for it to recognize the “current” page other than creating 5 different nav bar lines in each page that I have and having it id=current? Thanks for the help