Site Error 404 .. not able to index says google analytics

It seems my Site Error 404 page is not getting added to added site maps, is this something that needs to be added while creating a site map of my website.

I was under the impression that a site map accumulates all pages affiliated with my .com site.

any input would be helpful.

Since Google changed its UA format to the new A4 program, my indexing is all out of wack.