I don't know, there are some slight differences in canvas font renderers between Firefox and Chrome even in unaccelerated browsers. Try to use exactly the same

I don't know, there are some slight differences in canvas font renderers between Firefox and Chrome even in unaccelerated browsers. Try to use exactly the same font settings as in Bespin. It may be that "10px Arial" is ok but "0.9em sans-serif" looks very different.