@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

#extensionsView richlistitem[selected=true] {
  background-image: none !important;
}

#extensionsView richlistitem:not([selected=true]) .addonIcon {
  height: 16px !important;
  width: 16px !important;
}

#extensionsView richlistitem:not([selected=true]) .addon-description {
  display: none !important;
}