As you probably know, IIS uses VBScript as the default scripting language for Active Server Pages. Very often, however, we've seen pages where a Web developer has still explicitly set the scripting language for an ASP page by using the @Language directive, like this:
<%@ Language = VBScript %>
In fact, there's a small but measurable performance degradation on pages where the scripting language is set explicitly, so unless you have a reason to change the scripting language for an individual page to something other than the default, you're much better off sticking to the default and omitting the @Language directive. This is particularly important in high-traffic sites.
Source: Jason Fisher
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