Howto fix the '/GetSecondsBeforeUserLogout' error in Umbraco

In some Umbraco installations there are very frequent calls to the service

/umbraco/webservices/legacyajaxcalls.asmx/GetSecondsBeforeUserLogout

This may leave errors like this

Request format is unrecognized for URL unexpectedly ending in '/GetSecondsBeforeUserLogout'.

Here is how to fix it

Insert the webServices section in your web.config

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

There, it works

You may get other errors from here on, but the webservice(s) should at least be accessible