Showing ellipse mask bug in Firefox 32.

The red square wont appear if you are experiencing the bug.

HTML

<svg width="0" height="0">
  <defs>
  <mask id="m1" maskUnits="objectBoundingBox" maskContentUnits="objectBoundingBox">
    <radialGradient id="g" gradientUnits="objectBoundingBox">
        <stop offset="0.1" stop-color="white" />
        <stop offset="1" stop-color="white" stop-opacity="0" />
    </radialGradient>
     <ellipse fill="url(#g)" cx="0" cy="1" rx="1" ry="0.8" />
     <ellipse fill="url(#g)" cx="1" cy="1" rx="1" ry="0.8" />
  </mask>
  </defs>
</svg>
<svg width="0" height="0">
  <defs>
  <mask id="m2" maskUnits="objectBoundingBox" maskContentUnits="objectBoundingBox">
    <radialGradient id="g" gradientUnits="objectBoundingBox">
        <stop offset="0.1" stop-color="white" />
        <stop offset="1" stop-color="white" stop-opacity="0" />
    </radialGradient>
     <circle fill="url(#g)" cx="0" cy="1" r="1" />
     <circle fill="url(#g)" cx="1" cy="1" r="1" />
  </mask>
  </defs>
</svg>
<span class="outline"><div style="background: red; width: 150px; height: 150px; mask: url(#m1);"></div></span>
<span class="outline"><div style="background: blue; width: 150px; height: 150px; mask: url(#m2);"></div></span>

CSS

body { background: #000; }
.outline { display: inline-block; border: 1px dotted white; }