My nine month old is sitting up q.well and rolls over from her back to her front - but that's about it! I've just been on a site that suggests baby's should be crawling between 6-10 months - but my little one appears to be nowhere near ready! She isn't very mobile at all apart from the odd roll (and then she complains when she's stuck on her tummy)! What is "normal?" in regards to development, do things generally develop at differing paces for each child? Help!