GitHub - jkeyes/baseline: HTML and CSS baseline grid tools and examples

The bookmarklet can be found here and it allows you to run Baseliner on any webpage.

<script src="baseliner.js"></script>
<script>
window.onload = function() {
    baseliner = new Baseliner(8);
}
</script>

// a black grid, 20 pixels high
baseliner = new Baseliner({'gridColor': [0, 0, 0, 255], 'gridHeight': 20 });
// a red grid, 10 pixels high
baseliner = new Baseliner({'gridColor': 'red'});
// a black grid, 24 pixels high, offset by 10 pixels
baseliner = new Baseliner({'gridHeight': 24, 'gridOffset': 10});