Use an customizable prefix, change it for your test environment.
I don't know ASP.net, so this would be it in, say... JSP:
---- something.jsp --------
...
<%! public static final PREFIX = "http://pohlidame.cz/"; %>
...
<a href="<%= PREFIX %>onas">Insolvenční rejstřík</a>
...
---------------------------
This is quite simplistic example. In component oriented frameworks, you create the links' href value somewhere in the controller tier. That might be the case of ASP.net.
But generally, it's a simple concatenation of the prefix plus your desired "relative" location.