I have CSS in an internal style tag in the header but with an id as in <style id="mks">...css ...</style>. Now I want to make this css external, let us say in “myfile.css”. The obvious thing to do is now to place a line like

<link rel="stylesheet" href="myfile.css">

in my HTML code, but what do I have to do for having the id="mks" still being valid?