This is a question that I've received today from a customer and the answer is
YES. 
If you have a .NET Web Service http://www.mydomain.com/myservice.asmx and you
type this url on your browser, a default page (provided by the .NET Framework)
is displayed to you: here you can see all the methods provided by your Web
Service. But how you can obtain a personalized page to the Web Service URL?
The answer is simple and comes from one of the many .NET methods that are not
so famous: the wsdlHelpGenerator element.
This element (placed on the Web.config file) permits you to specify the XML
Web service Help page (an .aspx file) that is displayed to a browser when the
browser navigates directly to a .asmx XML Web
services page.
You can create your personalized page (for example with a logo, personalized
text etc.), open your Web.config file and place this section:
<configuration>
<system.web>
<webServices>
<wsdlHelpGenerator href="mypage/MyServiceHelpPage.aspx"/>
</webServices>
</system.web>
</configuration>
That's all... now if you open the Web Service's URL with your browser, you'll
obtain your new page. More simple than what you think... 
P.S. Remember that the value of href
is a file path, not a URL.