Doing it with style
The 'box' containing the animation has a shadow applied, not much use.
This uses the CSS filter to apply the drop shadow and applies this to the images within the animation.
This uses an inline SVG filter which applies the drop shadow to the images within the animation.
The inline method is necessary for IE10+.
This demonstrations show two methods of implementing a 'drop shadow', not to be confused with a 'box-shadow', on a transparent gif animation.
The first method is to use just CSS, and this works in IE7/8/9 (although the drop shadow is not very good), Chrome (using filter), Safari (using filter), Opera (using filter) and Firefox (using filter with SVG).
The second method uses inline SVG, filter and image which works in Firefox, Chrome, Safari, Opera and IE10+.
CSS 'filter' is such a useful style it is a pity that it is only supported in Chrome, Safari and Opera.
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