<p>Why does tempuri.org exist?  Why does each XML Webservice require its own namespace, unique from any other on the web?</p>

Unfortunately the
```
tempuri.org
```
URL now just redirects to Bing.
You can see what it used to render via
```
archive.org
```
:
https://web.archive.org/web/20090304024056/http://tempuri.org/
To quote:
Each XML Web Service needs a unique namespace in order for client
  applications to distinguish it from other services on the Web.  By
  default, ASP.Net Web Services use
http://tempuri.org/
for this
  purpose.  While this suitable for XML Web Services under development,
  published services should use a unique, permanent namespace.
Your XML Web Service should be identified by a namespace that you
  control.  For example, you can use your company's Internet domain name
  as part of the namespace.  Although many namespaces look like URLs,
  they need not point to actual resources on the Web.
For XML Web Services creating[sic] using ASP.NET, the default namespace can
  be changed using the WebService attribute's Namespace property.  The
  WebService attribute is applied to the class that contains the XML Web
  Service methods.  Below is a code example that sets the namespace to
  "
http://microsoft.com/webservices/
":
C#
```
```
[WebService(Namespace="http://microsoft.com/webservices/")]
public class MyWebService {
   // implementation
}
```
```
Visual Basic.NET
```
```
<WebService(Namespace:="http://microsoft.com/webservices/")> Public Class MyWebService
    ' implementation
End Class
```
```
Visual J#.NET
```
```
/**@attribute WebService(Namespace="http://microsoft.com/webservices/")*/
public class MyWebService {
    // implementation
}
```
```
It's also worth reading section 'A 1.3 Generating URIs' at:
http://www.w3.org/TR/wsdl#_Toc492291092