children all develop at different times but there are time parameters during which one would expect a milestone to be achieved

during which one would expect a milestone to be achieved. Walking is expected anywhere between 9 months to 12 months but can occur outside those times. What is important is being aware of developmental milestones so that if a child is not on target early intervention can be initiated. The goal is to provide every child with the tools to achieve to their potential.
what are your thoughts?
Why Act Early if You're Concerned about Development