Although it is possible to place style sheet links (links to CSS files) anywhere in the body of a web page, it is a best practice to place your style sheet link in the head area of the document.
By placing the reference link in the head area, your web pages will appear to load faster because it will allow the web page to render progressively. Progressive rendering means that a web page will load items as they are ready. This practice is optimal for frontend web designers that care about load times or need to display a lot of content within a web page.
Some of the problems associated with referring style sheets in the body of a document may include having a user momentarily see a blank white screen or a brief glimpse of unstyled content. Internet Explorer will have greater issues with CSS loaded outside of the head area than other browsers.