Now that "Content" is a string and any HTML element can be identified by using regular expression as an HTML element would have a certain pattern in that string variable.
Example :
<br />
String Content = "<link type="text/css" rel="stylesheet" href="http:
<link type="text/css" rel="stylesheet" href="http://s.codeproject.com/App_Themes/CodeProject/CSS/jquery.autocomplete.min.css?dt=2.8.140216.1"><br />
"<br />
A link here is havng a patten as mentioned "<" followed by word "link" then some string and follwed by ">". You need to write regex to extract such matching and manipulate them.
Let me know if that helps.