You have some CSS code that you want to use on all the web pages in your corporate web site. The best way to do this is to $...$

put the CSS in the shead$>$ tag of the web portal page so it can be accessed by all the other pages

write the CSS code once, and copy this into each page's HTML file

use an external css file located in the folder with the web pages

any of the above are good ways to do this