.net sucks?

I made at least 15+ websites over the last 4 months and always when i try to rank these domains they are up on page 1 then after a few days they disappear and never come back... who else got this? This is crazy? Only org and com seem to stay in serps for me why?

I think u posted wrong Title. It should be YOUR WORK SUCKS.

Then why all the sites with com and org do it fine for me?