<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
</head>
<body>
<svg>
<defs>
<linearGradient id="grad1" x1="0%" y1="0%" x2="100%" y2="0%">
<stop offset="0%" style="stop-color:rgb(255,255,0);stop-opacity:1" />
<stop offset="100%" style="stop-color:rgb(255,0,0);stop-opacity:1" />
</linearGradient>
</defs>
<circle cx="50" cy="50" r="40" fill="url(#grad1)" />
</svg>
</body>
</html>