Mini laptops usually have a screen size of 7 to 10 inches. Some 11.6 inch screens still get lumped into the mini laptop segment, but at that sie they're starting to become regular laptops, not minis. Keep in mind that screen size is measured from the top left hand corner of the screen to the bottom right hand corner — so that 7 inches is the longest length of the screen, or the diagonal length of the screen.
Mini laptops tend to weigh around 2-3 pounds and will have anywhere between 3 and 8 hours of battery life. They can be had for as little as $150 (new, from Amazon.com) or as much as $700 if you get a really souped-up machine.
Keep in mind that you get what you pay for with netbooks or mini laptops, and unless you are going to be using them for nothing more than surfing the internet and checking email, or writing, or very simple office work, a netbook probably won't work for you. In other words, if you're going to be using anything more than word, excel and an internet browser, it might be a much better idea to just go get a regular laptop.
That said, definitely go “meet” a model of your future netbook before you buy it. For some people, especially older people, a 7 inch screen is going to be almost unusable. And even for younger folk, a 7 inch screen is too small to see a whole web page — you'll be doing a lot of scrolling, and that tiny little mouse pad may end up hurting your hands if you spend too many hours using your mini laptop computer for lengthy work (or play). It barely needs to be said, but I'll say it anyway — don't expect to do much or any gaming or image manipulation on these mini laptops. They are simply not made for it.
Another major limitation of mini laptop computers is the keyboards. This is especially tough, again, on older people, or even grown adults. Between the tiny screen and the hard-to-use keyboard, it may become really obvious really fast that a tiny computer is not going to work for you.
But after all those warnings, should anyone get a mini? Yes! If you're already used to texting, or working on a laptop that's 13 inches or less, using a mini laptop computer will be fine for checking email and the internet, writing and even doing light office work with Excel and Powerpoint. They're also terrific for traveling, because minis aren't just light, but they're also cheap — you'll cry less if your $200 mini laptop gets stolen than you would if your $2000 laptop did.
Upgrading the battery for your mini laptop computer is a good use of money. Most come with 3 cell batteries, but a 6 cell one will hold a charge longer and give you more charges before it goes “kaput”. The average laptop battery, by the way, only has about 500 charges in it before it starts to seriously fade and needs to be replaced.