Avoid using the water you used to steam the carrots to thin the carrots. While this is a great idea with most fruits and vegetables, carrots have high nitrate (which can be beneficial, but also poisonous to some degree) levels, and the nitrates seep into the steaming water. Instead of using the water from steaming, consider adding some breast milk, formula, or other fresh water to thin the carrots. Some Moms choose to feed baby jarred carrots instead of homemade because the packaged carrots lose more nitrates in the processing.
From what I have read, it is generally recommended NOT to feed a baby younger than 3 months old carrots. I also found that most babies should be able to handle carrots at 6 months of age.
I also know that for Gabe here, carrots may have caused him a bit of flatulence (and constipation-like symptoms -- as in he didn't go until this afternoon since Sunday night when carrots were introduced. We were about to resort to the doctor's orders for prunes, but he finally went... at the babysitter's!)
You can read some more specific information about homemade carrots for baby here and here and here.
"Hello!" from my little carrot.