Netbooks are designed for pure mobility. They are, however, more fragile and vulnerable to physical damage than their full-size laptop cousins, which have a heavy-duty build. Keep your netbook fully protected by carrying it in a sturdy, well-padded netbook case when you are out and about. The more padding your netbook case has, the better the protection it will provide.
You may also use a netbook sleeve but, while it may protect against scuffs, dirt and scratches, this type of case is really more decorative than protective. A netbook sleeve can, however, provide additional protection for the netbook inside your suitcase or backpack.