Now another 2 of my sites are missing again. These were steadily climbing up the SERPs for their main keyword and then all of sudden they are gone for that specific keyword I was building backlinks for. The sites are indexed and all and they are ranking for other terms, but for the main keyword that I used as anchor text to build backlinks for the site is no where in the SERPs.
What causes these sites to go missing from the SERPs at times? And I know sites will shift and move around and come back, but usually that is only like a few days or a week, but I've noticed my sites to go missing for like over month or 2 at times.
Any insight on what exactly causes this to happen?