why does the price down ?

there is bad news about pxc,isnt it ?

There's no bad news. All you see is that one person sold some of his PXC. He must have been in a hurry to get some cash so he sold below market price. If people are starting to outbid eachothers with lower and lower prices, then you start worrying.
But that actually rarely happens with starting coins like this.
We all know to hang on to them because PXC has so much momentum right now it has no where to go but up.
To prove this : WTB 1 K PXC for 19 LTC !