If you have 10 different stylesheets for a given design, how would you integrate them into the site?
Every CSS file we use on a website will add time to our page load speed. CSS will not care where it is at or how many files it is in. However in most cases we can have a combination of two or more CSS files together.Developers handle this situation in multiple ways. Few of them simple combine by copy pasting one from another.
The other possible way to combine CSS files using YUI Compresser, that combines CSS and minimizes code and is good for performance. Few handle this by using build tools like GRUNT.
One CSS file that contains all the styles of the separate CSS files combined will work just as well and improve the page speed. Putting all of the CSS into one file substantially reduces the amount of time it takes to load our web pages because we are reducing the amount.