How conditional Css for all IE browsers?

Is this correct to specify a css snippet for "all" IE version browsers:

  @if user.agent ie6 {
    .block {
       background-color: #FF00FF;
    }
  } 

Or must I include all IE versions like ie6, ie7, ie8, etc...?

I am not sure as I read different stories about it in the forum link here (below). In some examples I see people only use ie6, but in some I see them using all IE user.agents constants as contained in UserAgent.gwt.xml.

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