All babies develop and mature at their own unique pace. Some are early at this and later at that. So we know, realistically, that we need to give a great deal of leeway.
But maybe something doesn't seem quite right. Maybe you're wondering if your child may have some kind of disorder, like cerebral palsy.
Here is a place to find some information about cerebral palsy symptoms. And here is some reassurance that if it should turn out that your child does have this disorder, that therapies and resources are available to your child, and to you as the parent.
"The vast majority of cerebral palsy symptoms include abnormal neonatal reflexes, hearing and vision loss, stiffness of muscles with awkward movements, extension of extremities when the infant is held upright, and scissoring of the lower limbs because of spasm of the muscles of the thigh. Some kids with cerebral palsy may also have slight to severe mental retardation. This is not always so, however. In fact, there are many people who have cerebral palsy that have normal mental capacities."
http://www.zimbio.com/Cerebral+palsy/articles/XtPgO4jOtsO/Close+Look+Cerebral+Palsy+Symptoms