No, child support is not tax deductible.
In the Personal Info section, you will be asked if you support another person. Be careful before you say "yes."
In some cases, the noncustodial parent can claim the child as a dependent on his tax return, but only if the custodial parent agrees and gives him a signed Form 8332 releasing her right to claim the child.
If that is not the case, then you should say no when asked about supporting another person, and you shouldn't claim the child as a dependent.