检测浏览器（比如IE）的版本号码是Web 开发最常遇到的问题之一， 以下总结几种检测IE版本号码的方法：
通过Javascript解释浏览器的 User-Agent 字符串：

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function getInternetExplorerVersion()  
// Returns the version of Internet Explorer or a -1  
// (indicating the use of another browser).  
{  
  var rv = -1; // Return value assumes failure.  
  if (navigator.appName == 'Microsoft Internet Explorer')  
  {  
    var ua = navigator.userAgent;  
    var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");  
    if (re.exec(ua) != null)  
      rv = parseFloat( RegExp.$1 );  
  }  
  return rv;  
}  
function checkVersion()  
{  
  var msg = "You're not using Internet Explorer.";  
  var ver = getInternetExplorerVersion();  
 
  if ( ver > -1 )  
  {  
    if ( ver >= 8.0 )   
      msg = "You're using a recent copy of Internet Explorer." 
    else 
      msg = "You should upgrade your copy of Internet Explorer.";  
  }  
  alert( msg );  
} 
function getInternetExplorerVersion()
// Returns the version of Internet Explorer or a -1
// (indicating the use of another browser).
{
  var rv = -1; // Return value assumes failure.
  if (navigator.appName == 'Microsoft Internet Explorer')
  {
    var ua = navigator.userAgent;
    var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
    if (re.exec(ua) != null)
      rv = parseFloat( RegExp.$1 );
  }
  return rv;
}
function checkVersion()
{
  var msg = "You're not using Internet Explorer.";
  var ver = getInternetExplorerVersion();
  if ( ver > -1 )
  {
    if ( ver >= 8.0 )
      msg = "You're using a recent copy of Internet Explorer."
    else
      msg = "You should upgrade your copy of Internet Explorer.";
  }
  alert( msg );
}
通过Javascript判断IE渲染引擎的的当前渲染模式：
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engine = null;  
if (window.navigator.appName == "Microsoft Internet Explorer")  
{  
   // This is an IE browser. What mode is the engine in?  
   if (document.documentMode) // IE8  
      engine = document.documentMode;  
   else // IE 5-7  
   {  
      engine = 5; // Assume quirks mode unless proven otherwise  
      if (document.compatMode)  
      {  
         if (document.compatMode == "CSS1Compat")  
            engine = 7; // standards mode  
      }  
   }  
   // the engine variable now contains the document compatibility mode.  
} 
engine = null;
if (window.navigator.appName == "Microsoft Internet Explorer")
{
   // This is an IE browser. What mode is the engine in?
   if (document.documentMode) // IE8
      engine = document.documentMode;
   else // IE 5-7
   {
      engine = 5; // Assume quirks mode unless proven otherwise
      if (document.compatMode)
      {
         if (document.compatMode == "CSS1Compat")
            engine = 7; // standards mode
      }
   }
   // the engine variable now contains the document compatibility mode.
}
通过ASP.NET 的 HttpBrowserCapabilities 对象:

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private float getInternetExplorerVersion()  
{  
  // Returns the version of Internet Explorer or a -1  
  // (indicating the use of another browser).  
  float rv = -1;  
  System.Web.HttpBrowserCapabilities browser = Request.Browser;  
  if (browser.Browser == "IE")  
    rv = (float)(browser.MajorVersion + browser.MinorVersion);  
  return rv;  
}  
 
private void Page_Load(object sender, System.EventArgs e)  
{  
  string msg;  
  double ver = getInternetExplorerVersion();  
  if (ver > 0.0)  
  {  
    if (ver >= 7.0)   
      msg = "You're using a recent version of Internet Explorer.";  
    else 
      msg = "You should upgrade your copy of Internet Explorer.";  
  }   
  else 
    msg = "You're not using Internet Explorer.";  
 
  Label1.Text = msg;  
} 
private float getInternetExplorerVersion()
{
  // Returns the version of Internet Explorer or a -1
  // (indicating the use of another browser).
  float rv = -1;
  System.Web.HttpBrowserCapabilities browser = Request.Browser;
  if (browser.Browser == "IE")
    rv = (float)(browser.MajorVersion + browser.MinorVersion);
  return rv;
}
private void Page_Load(object sender, System.EventArgs e)
{
  string msg;
  double ver = getInternetExplorerVersion();
  if (ver > 0.0)
  {
    if (ver >= 7.0)
      msg = "You're using a recent version of Internet Explorer.";
    else
      msg = "You should upgrade your copy of Internet Explorer.";
  }
  else
    msg = "You're not using Internet Explorer.";
  Label1.Text = msg;
}

通过HTML的扩展注释语句：

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<!--[if gte IE 8]> 
<p>You're using a recent version of Internet Explorer.</p> 
<![endif]--> 
 
<!--[if lt IE 7]> 
<p>Hm. You should upgrade your copy of Internet Explorer.</p> 
<![endif]--> 
 
<![if !IE]> 
<p>You're not using Internet Explorer.</p> 
<![endif]> 
<!--[if gte IE 8]>
<p>You're using a recent version of Internet Explorer.</p>
<![endif]-->
<!--[if lt IE 7]>
<p>Hm. You should upgrade your copy of Internet Explorer.</p>
<![endif]-->
<![if !IE]>
<p>You're not using Internet Explorer.</p>
<![endif]>
 
有些方法在之前的blog文章提过
MSDN参考文章：(1), (2)