If you are using Compass, you are probably also at least playing with media queries and Responsive web design.

Have you tried nesting media queries in compass? Just nest your conditional styles in a media query, and compass will output a normal media query for your responsive pleasure.

This is a great alternative to moving to a separate part of your file or switching files and finding the right place in your media query for your new rule.

Compass Nested Media Queries

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Compass Nested Media Queries
nested_media_queries.scss
#sidebar    {
    width: 100%;

    @media only screen and ( min-width: 480px; )    {
        width: 33.33333%;
        float: right;
    }
}