This At-Rule syntax imports a style sheet fragment file to the
current style sheet. It may be used in External and Embedded style
sheets, but not with inline styles. Furthermore, multiple fragments can
be imported in to a single style sheet, but all @import statements must
occur before any style declaration Rule-Sets in the style sheet.
An optional, case-insensitive argument can be specified after the URL of
the fragment indicating one or more target media where the fragment should
be applied (the default if no media is specified is "all".) Specifying
media dependent styles via @import can be more efficient than
@media At-Rules, because unneeded style fragments
do not need to be downloaded or parsed in the @import case.