The @cc_on statement activates conditional compilation within comments in a script.
It is not common to use conditional compilation variables in scripts written for ASP or ASP.NET pages or command-line programs because the capabilities of the compilers can be determined by using other methods.
When you write a script for a Web page, always put conditional compilation code in comments. This enables hosts that do not support conditional compilation to ignore it.
It is strongly recommended that you use the @cc_on statement in a comment, so that browsers that do not support conditional compilation will accept your script as valid syntax:
An @if or @set statement outside of a comment also activates conditional compilation.