Originally Posted by DaleDe
I suspect that ADE cannot interpret what you want. What is 2.5 times bigger than itself? 2.5em makes no sense since you are asking it to make itself 2.5 bigger but then that would be an em. I suspect font-size units need to be something other than font-size.
This is actually fine. I use it for quite some time. 1em will be interpreted as 100%, so 2.5em is equal to 250%.