ASP.NET fails to detect IE10 causing _doPostBack is undefined JavaScript error

Should you encounter _doPostBack is undefined JavaScript error on IE 10, it is because there is a bug in the browser definition files that shipped with .NET 2.0 and .NET 4.

Scott Hanselman published two ways to fix this: one is a machine-wide fix, the other is a way to fix individual sites. The replacement of the "fixed" ie.browser file will supposedly resolve the problem but it somehow didn't quite work for me. If that file didn't work for you, you may wish to use the below instead.

~\App_Browsers\ie.browser

<browsers>
    <!-- Mozilla/5.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4325) -->
    <browser id="IE6Plus" parentID="IE">
        <identification>
            <capability name="majorversion" match="^[6-9]|\d{2,}$" />
        </identification>

        <capabilities>
            <capability name="ecmascriptversion"    value="3.0" />
            <capability name="jscriptversion"       value="5.6" />
            <capability name="javascript"           value="true" />
            <capability name="javascriptversion"    value="1.5" />
            <capability name="msdomversion"         value="${majorversion}.${minorversion}" />
            <capability name="w3cdomversion"        value="1.0" />
            <capability name="ExchangeOmaSupported" value="true" />
            <capability name="activexcontrols"      value="true" />
            <capability name="backgroundsounds"     value="true" />
            <capability name="cookies"              value="true" />
            <capability name="frames"               value="true" />
            <capability name="javaapplets"          value="true" />
            <capability name="supportsCallback"     value="true" />
            <capability name="supportsFileUpload"   value="true" />
            <capability name="supportsMultilineTextBoxDisplay" value="true" />
            <capability name="supportsMaintainScrollPositionOnPostback" value="true" />
            <capability name="supportsVCard"        value="true" />
            <capability name="supportsXmlHttp"      value="true" />
            <capability name="tables"               value="true" />
            <capability name="supportsAccessKeyAttribute"    value="true" />
            <capability name="tagwriter"            value="System.Web.UI.HtmlTextWriter" />
            <capability name="vbscript"             value="true" />
        </capabilities>
    </browser>

    <!-- Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0;) -->
    <browser id="IE6to9" parentID="IE6Plus">
      <identification>
        <capability name="majorversion" match="^[6-9]$" />
      </identification>
    </browser>

    <!-- Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0;) -->
    <browser id="IE7" parentID="IE6to9">
        <identification>
            <capability name="majorversion" match="^7$" />
        </identification>
        <capabilities>
            <capability name="jscriptversion" value="5.7" />
        </capabilities>
    </browser>

    <!-- Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729) -->
    <browser id="IE8" parentID="IE6to9">
        <identification>
            <capability name="majorversion" match="^8$" />
        </identification>
        <capabilities>
            <capability name="jscriptversion" value="6.0" />
        </capabilities>
    </browser>

  <!-- Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729) -->
  <browser id="IE9" parentID="IE6to9">
    <identification>
      <capability name="majorversion" match="^9$" />
    </identification>
    <capabilities>
      <capability name="jscriptversion" value="6.0" />
    </capabilities>
  </browser>

  <!-- Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0) -->
  <browser id="IE10Plus" parentID="IE6Plus">
    <identification>
      <capability name="majorversion" match="\d{2,}" />
    </identification>
    <capabilities>
      <capability name="jscriptversion" value="6.0" />
    </capabilities>
  </browser>

  <gateway id="IEbeta" parentID="IE">
        <identification>
            <capability name="letters" match="^([bB]|ab)" />
        </identification>

        <capture>
        </capture>

        <capabilities>
            <capability name="beta"    value="true" />
        </capabilities>
    </gateway>
</browsers>