Use the VaryByHeader to create new cached versions of a page in case of new browser header changes.
Several standard browser headers are transmitted with each page request, including
Accept-Language: a list of languages.
User-Agent: type of device making the request.
Cookie: the browser cookies created in the current domain.
<%@ Page Language="C#" %>
<%@ OutputCache Duration="3600" VaryByParam="none" VaryByHeader="User-Agent" %>
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Vary By Header
<%= DateTime.Now.ToString("T") %>
<%= Request.UserAgent %>