Using this the samples located here I’ve put this together:
The code is located on jsFiddle.net. If everything works when you run the sample, you should see a button with a question mark and clicking on that button the and the bubble should pop out.
The two things I can’t seem to figure out right now is getting a 1px border on the triangle and vertically centering the triangle on the left edge.
For the line thickness of the triangle, change the
top,leftandborder-widthvalues for the inner triangle so it’s just 1px smaller than the larger triangle.