converting svg code to svg file

I have a svg image that looks like this:   http://jsfiddle.net/sa4J4/

This is the code for my svg image.

<svg width="100" height="100">
  <circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" />
</svg>

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How do I convert this svg code to a file with a .svg file extension?

So for example,  I want to save it to a svg file called YellowCircle.svg


See I want to use this svg image on a web page but I don't want to use the code I just want to use the file.

See on my web page I want to use it like this:

 <a href="http://www.google.com"><img src="images/YellowCircle.svg"></a> 

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