解决ie8下，不支持video、audio的问题

 <audio controls="controls" preload="none" src="@SiteUrls.Instance().AttachmentAudioUrl(Model)">
     <embed src="@SiteUrls.Instance().AttachmentAudioUrl(Model)" height="44" />
 </audio>

  <video width="618" height="430" controls="controls" preload="none" autoplay="autoplay">
     　　<source type="video/mp4" src="@SiteUrls.Instance().AttachmentVideoUrl(attachment)" />
         <object width="618" height="430" type="application/x-shockwave-flash" data="~/Scripts/mediaelement/flashmediaelement.swf">
             <param name="movie" value="~/Scripts/mediaelement/flashmediaelement.swf" />
             <param name="flashvars" value="controls=true&amp;file=@SiteUrls.Instance().AttachmentVideoUrl(attachment)" />
             <param name="wmode" value="opaque">
         </object>
  </video>