It’s because they are inline elements with resizable height
(most inline
elements are not explicitly resizable). If you set them to display: block;
the gap goes away. You can also set vertical-align: top;
to achieve the same result.
Demo: http://jsfiddle.net/ThinkingStiff/F2LAK/
HTML:
<div class="container">
<canvas width="200" height="100"></canvas>
</div>
<div class="container">
<canvas id="block" width="200" height="100"></canvas>
</div>
CSS:
.container {
border: 1px solid blue;
}
canvas {
border: 1px solid red;
}
#block {
display: block;
}
Output: