Compatible in IE7 in IE8

<system.webServer>
    <!-- For now..... lets be safe and put IE8 in IE7 compatibility mode-->
    <httpProtocol>
      <customHeaders>
        <clear />
        <add name="X-UA-Compatible" value="IE=EmulateIE7" />
      </customHeaders>
    </httpProtocol>
</system.webServer>

Page Load

Page.Header.Controls.AddAt(0, new HtmlMeta { HttpEquiv = "X-UA-Compatible", Content = "IE=EmulateIE7" });