Not a SVG file!
NOTE: the SVG file URL must point to the file itself, not to its description page. For example, http://upload.wikimedia.org/wikipedia/commons/8/8a/Planetary_transit.svg is a valid URL. You may get this by going to the image description page, right clicking over the SVG and selecting "Copy Link Location" or similar in your browser's menu.
Questions, comments, suggestiong and bug reports are welcome at my talk page.