I have a problem with my domain, help!

Ok so here is my problem, and i have no idea what to do
Well the thing is that my domain shows twice in the tab box... like this: www.DomainNameDomainName.com
Any suggestions how i can fix this.
Also im having problem with 404 pages, i want to delete them and im not sure how, i already deleted them and i cant find them in my website but google is still finding them, and i resubmit the sight map but still....
Thanks!!!

any help form someone ?