so i posted my pixel art at 7/5/17 didnt get approved yet and i saw pixel art that was posted after i posted mine and got approved this is the pixel art -> http://pixeljoint.com/pixelart/113995.htm
any idea why?
once it took more than a week untill my pixel art was approved

A few factors contribute to a piece sitting on the queue a while:
- There is a public voting system. Pieces that get a unanimous "yes" response get approved more quickly. Pieces that get a few "no" votes take longer, the mods wait until there is a strong consensus.
- People might be more reluctant to vote on repeat submissions like yours, either because they think it's suspicious or because they don't notice that it's a new submission and think they voted already.
- Artwork with interesting, appealing thumbnails probably accumulates votes faster because it gets people to click and see. Not everyone has the time to vote on everything in the queue, so some people are selective.
- The submissions are not approved or voted on in chronological order. If there is a flood of submissions after yours, your submission gets harder for people to come across. The mods try to stay on top of the queue but some pieces end up pushed back.
- Due to a flaw with PJ, the mods are only able to vote on a subset of all submissions. If there was a flood of submissions after yours, it's possible your piece got pushed past the point where the mods can't approve it until some of the more recent submissions are cleared off the queue.
- On top of all this, the mods try to pace their approvals so that every submission gets some time on the front page, so they try not to approve too many submissions at once. This can slow things down when there are a lot of submissions.