How do I combine multiple sheets into one?

Multiple sheets can be combined into by using the <link> tag and the with the title attribute. The title value allows one or more <link> tags to link with each other. After combination that theme will be applied as combined and will be shown to the user. The syntax of it will be as follows:
<link rel= “text/css” href="default.css" title="combined">
<link rel= “text/css” href="style.css" title="combined">
<link rel= “text/css” href="para.css" title="combined">

Another way to combine the style sheets is the use of import which can be used in the <style> tag and the syntax can be given as follows:
@import url(site_url);