You should never use more than one script language on the same ASP page, for example by mixing pieces of VBScript with portions of JavaScript. The reason is that there is a limit to the number of script engines that ASP can cache.

When IIS processes an ASP file, it parses the script code and caches the result of this parsing in a so-called script engine. Unfortunately, this cached engines cannot be shared among multiple clients at the same time, therefore even if a given page is being accessed by 10 clients, IIS must cache ten instances of the same script engine. Of course, if the page uses two script languages – such as VBScript and JavaScript – IIS must waste two script engines for each client browsing that page, thus reducing the total number of cached ASP files and the site’s scalability.