Conditional compilation is supported in all versions of Internet Explorer prior to Internet Explorer 11. Starting with Internet Explorer 11 Standards mode, and in Windows Store apps, conditional compilation is not supported.
Always place conditional compilation code in comments, so that hosts (like Netscape Navigator) that do not support conditional compilation will ignore it. Here is an example.
This example uses special comment delimiters that are used only if conditional compilation is activated by the @cc_on statement. Scripting engines that do not support conditional compilation see only the message that says conditional compilation is not supported.