Regression

My baby was walking confidently and well, but since he had a cold he has stopped walking altogether and is crawling again. Should I be worried?

It is perfectly normal for babies to regress in any behaviour. Sickness is a usual cause of regression. A bad fall or other bad experience can also cause this to happen. He is probably feeling off-colour still and needing to be babied a bit. In all likelihood, as soon as he feels better he will be up and off again at top speed.