Using a third-party flash on a nikon d90?

I'm interested in buying a certain third-party flash for my d90. The flash can zoom, tilt, rotate and has a diffuser built in. The flash has only one button on it which is the on and off switch. It doesn't have an lcd, but it does have a sticker with a bunch of numbers (it's a manual flash). I would have given a better description of what was on the sticker but I was in a hurry so I didn't have time to read the sticker.

I'm not sure what the name is. It's not a big brand like nissin or yongnuo.

So what I'm wondering is: Can my camera control the flash? I read somewhere that you can't control third party flashes from your camera so I want to double check.

And what are the pros and cons of buying a third party flash?

I know that someone is probably going to tell me to buy a nikon flash, but I can't afford it at the moment. I will be getting one in the future.

Added (1). @John P

I did ask the sales person about that, and he said that it won't fry the camera.

Make sure the flash has a trigger voltage of 5 volts or less. Probably the Yongnuos and Nissins have that low voltage, but check. If it is an 'unknown brand' then be very careful. If you use a flash with higher trigger voltage you risk frying the circuits in the camera, which is a lot more expensive than a cheap flashgun.

Don't expect a cheap brand to offer the full works of control facilities that a Nikon flash would offer. Maybe it will, chances are that it won't. Only by trying it on the camera (having checked the trigger voltage!) will you know for sure.

1. Check the trigger voltage.
2. The centre pin on the hotshoe transmits the 'fire' signal - all the others are for TTL info for dedicated TTL flashes, so yes, you CAN fire the flash from your camera.
3. You will have to set the flash power output manually on the flash AND set your exposure manually on the camera. Don't forget you can't shoot above your max sync speed (about 1/200 sec shutter speed).

Your camera's only control of a such a flash is to tell it when to fire. Everything else you have to do yourself.

A make and model would be most helpful… And Yongnuo and Nissin are not "big" brands, by the way. Yongnuo earned it's name from being cheap. Nissin has grown into a pretty decent off-brand, but is still not a name like Sunpak or Vivitar or Metz.

The numbers were a chart of flash power to aperture to range, if it was a manual flash, or the same thing for an auto thyristor type flash. Auto flashes have a built-in sensor to control flash output, which usually works better than most TTL systems.

The only real con side is that you must know how to shoot in manual mode. Since the camera won't know the flash is there, it doesn't take a manual flash into account when calculating exposure, and all your shots will be overexposed in anything but manual mode. This is not a bad thing, unless you only shoot in green box auto. In that case, such a flash is useless.