In case you didn't know, AA stands for anti-aliasing. AA is a smoothing technique used to make things less choppy, or blend better with other colors like the first post on this forum:

http://www.vbforums.com/showthread.php?t=285163  

Notice how he uses other colors to make the red line blend better with the white background. Another good example of how anti-aliasing effects the pixels is this website:

http://www.pantherproducts.co.uk/Articles/Graphics/anti_aliasing.shtml

As you can see the letter on the left (the a) is much more jagged than the one on the right.

The lines aren't too bad, but could be improved in some places.  You've got a lot of banding and might want to check some shading tutorials.  Not bad for someone just starting out! 

That's it

You'll want to do this to anything where the BG is not needed, k. PJ users use all kinds of different colored themes which is why transparent BGs are a rule. Sometimes you need a special color BG so this is fine too sometimes, like when a technique called AA is used.

You'll probably want to look into tutorials (see links and forum) on how to make cleaner pixel lines and draw better metal surfaces so that your pixels can improve. A great place to start is with the n00btorial thread which covers a lot of basic pixelart stuff.

thanks i wish good luck to you in helping other people

Considering you are new its good enough. I'm sure you'll get better and better with time. The forum has a WIP (Work In Progress) section for you to get feedback, help and get questions answered before you upload to the gallery. This way its the best it can be and you learn new stuff along the way.

To make a BG transparent you'll want to color whatever will be transparent to a color not used anywhere else in the art (let's say red in this case). Then upload your pic using iaza (there are other online utilities and even free programs that do this too. Check out and look around the forum for all kinds of good stuff) once you have uploaded follow the directions (I think you just touch the color you want transparent) and that's it.

Then just hit the  'edit it' link up there ^ and walla!

so how do i remove the background and do you think its good?

yeah but how do i remove the background when im on the iaza site

Sorry about that :(

Once done hit 'edit it' link under the art to upload the new file.

Useless BGs is a Pixeljoint art submission rule.

where on iaza do i remove the background of a image

BG is background.  Get rid of the black behind the image and resubmit the picture. 

whats BG plz tell me and why does it affect my stuff

Please remove BG. Use www.iaza.com or some online utility if your program/app can't do so.