I code therefore I am.

HTTP GET for ASP.NET Webservices

It’s disabled by default and to enable it, add this to the web.config

<configuration>
    <system.web>
    <webServices>
        <protocols>
            <add name="HttpGet"/>
            <add name="HttpPost"/>
        </protocols>
    </webServices>
    </system.web>
</configuration>

Alternatively, you can enable these protocols in the Machine.config

<protocols>
	<add name="HttpSoap"/>
	<add name="HttpPost"/>
	<add name="HttpGet"/> 
	<add name="HttpPostLocalhost"/>
      <!-- Documentation enables the documentation/test pages -->
	<add name="Documentation"/>
</protocols>

[source: INFO: HTTP GET and HTTP POST Are Disabled by Default]