^^^ Also using a lifting belt is a matter of preference.. It does have it's pro's and con's though. It can help support the load your lifting and help with form and for people with a back it can make the squat a little more practical.. It's the supporting of the load though that makes me steer away from lifting belts. Without it, more of your smaller supporting muscles have to work to keep your body straight and your form perfect. A belt can also assist you in lifting a little more weight, but unless your aim is to lift more as apposed to putting on weight, it shouldn't matter what weight your lifting, as long as your KO'd by the 20th rep ;-) ( Joe_ice - that's how I like my squats,,, I'll only push myself once a fortnight like that.. But after I get that 20th rep out I have to lay on the floor for 2 minutes until I can move my legs again The joys of training hard!)
Anyway, that's just my 2 cents on weight belts but i've used them in the past while i've been working through minor injuries and they have helped me steer clear of some major ones..
Good luck with your squats though.. They are probably the most beneficial exercise to gain all over body mass...