You can attach external style sheets to a page using either link or import (or both).

Which is better? How to decide?

The topic has been much debated; see the links below for details.

Bottom line: link appears to be the best choice when two or more external style sheets are attached to a page, because download time is longer with import.

What's the Difference Between @import and link for CSS? – CSS FAQ
don't use @import | High Performance Web Sites
<link> vs @import
css – @import or <link> for importing stylesheets? – Stack Overflow
Link versus import –
Import or Link? CSS forum at WebmasterWorld
Best Practices for Speeding Up Your Web Site
4 methods of adding CSS to HTML: link, embed, inline and import
Difference between @import and link in CSS – Stack Overflow
Media types
Faster Page Loads – Bundle Your CSS and Javascript » SitePoint
Ultimate CSS Gradient Generator –
Minimize round-trip times
html – CSS import or <link rel…> with "media" attribute – Stack Overflow
@import Rule
Style Sheets in HTML documents
CSS Universe – Tips, Hacks: link vs @import
Decisions CSS Developers Need to Make
A List Apart: Articles: Progressive Enhancement with CSS
css – Using both <link> and @import to import the same stylesheet …
Digital Web Magazine – CSS Styling for Print and Other Media
Assigning property values, Cascading, and Inheritance
Media-Specific CSS Tutorial – Screen and Print Stylesheets
Bulletproof Mobile Device Detection and Style Sheets without User …
Improving Code Readability With CSS Styleguides – Smashing Coding