Using CSS borders, you can create play and pause icons with full browser compatibility, no images, and no extra http requests. Each one uses just one <div> and simple CSS.

Here are the icons:



If you have box-sizing: content-box set (default), use this CSS:

.play {
width: 0;
height: 0;
border-top: 8px solid transparent;
border-left: 12px solid #000;
border-bottom: 8px solid transparent;
}
.pause {
width: 4px;
height: 16px;
border-right: 4px solid #000;
border-left: 4px solid #000;
}
If you have box-sizing: border-box set, use this CSS:

.play {
width: 12px;
height: 16px;
border-top: 8px solid transparent;
border-left: 12px solid #000;
border-bottom: 8px solid transparent;
}
.pause {
width: 12px;
height: 16px;
border-right: 4px solid #000;
border-left: 4px solid #000;
}
To make them larger, increase the width and height and make sure to adjust the borders accordingly.