Filter elements are never rendered directly; their only usage is as something that can be referenced using the filter property. Be aware that filter elements are available for referencing even when the display property on the filter element or any of its ancestors is set to none.
In the following example, a previously defined Gaussian_Blur filter (that is, filter:url(#Gaussian_Blur)"/>) is being applied to an SVG ellipse:
<ellipse cx="200" cy="150" rx="70" ry="40" style="fill:#ff0000; stroke:#000000; stroke-width:2; filter:url(#Gaussian_Blur)"/>
Microsoft Developer Network: [Windows Internet Explorer API reference Article]