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VI Snippets are a new way to store, share and reuse small portions of LabVIEW code.
Read more on http://zone.ni.com/devzone/cda/tut/p/id/9330
Firefox and some other browsers behave differently to Internet Explorer in the way they handle dragged images.
You will notice if you drag a VI Snippet from Firefox directly to LabVIEW you will get the URL of the image rather than the code you expected.
An easy way to get around this is to drag the image to your desktop or a folder first, and then drag the image from your desktop to LabVIEW.