Does anyone know if Firebug rounds the offset top and left when they give us the below panel?
The reason I ask is because I am having trouble with using offsets that have decimal places and I am wondering whether Firebug rounds or floors these values.
I tried to have a look at the source code but couldn’t pinpoint where offset calculations were being made.
Any help appreciated.

According to the firebug source on SVN, the offset values are parsed as integers. Also have a look at this.
I’m not 100% what Firebug doesbut when I deal with decimal values for pixels I always floor because rounding up may break the layout.This question may also help: Are the decimal places in a CSS width respected?