?  To set the UI culture and culture for all pages, add a
globalization section to the Web.config file, and then set
the uiculture and culture attributes, as shown in the
following example:
<globalization uiculture="es" culture="es-MX" />
?  To set the UI culture and culture for an individual page,
set the Culture and UICulture attributes of the @ Page
directive, as shown in the following example:
<%@ Page UICulture="es" Culture="es-MX" %>

add a
<system.web> 
<globalization uiculture="" culture="" />

in the web. config section

or set both through dynamic coding..

Eg:
set uiculture in InitializeCulture page method override. 
protected override void InitializeCulture() 
{
      this.UICulture = "he";
}

Setting up a language are of 2 types

one is compilation language of webapplication for which 
you can try with this code

<configuration>
    <system.web>
	<compilation defaultLanguage"VB"></compilation>
    </system.web>
</configuration>

Second is regional / culture language it can be set with 
the following code

<system.web>
    <globalization uiCulture="en" culture="en-GB" />
    <!-- more stuff-->
</system.web>