Extract to class

If a rule is repeated, extract it to a class and use that instead.

From:

#system-admin-icon {
    display:block;
    width:160px;
    height:160px;
    background-image:url( '/static/images/admin_export.png' );
}

#system-thor-icon {
    display:block;
    width:160px;
    height:160px;
    background-image:url( '/static/images/thor_export.png' );
}

#system-toms-icon {
    display:block;
    width:160px;
    height:160px;
    background-image:url( '/static/images/toms_export.png' );
}

To

.system-icon {
    display:block;
    width:160px;
    height:160px;
}

#system-admin-icon {
    background-image:url( '/static/images/admin_export.png' );
}

#system-thor-icon {
    background-image:url( '/static/images/thor_export.png' );
}

#system-toms-icon {
    background-image:url( '/static/images/toms_export.png' );
}

Why?

Classes encourage reusability and modularity.