Error 404-Page NOT Found

I was a nice person, when the theme asked me to put up a featured image I did for my 'articles' page, which is my post page. However, since I did that the articles page shows the error: Error 404-Page NOT Found How can I fix this? Am I not able to use the articles page in my slidebar now? Thanks in advance, I hope it van be helped fast.. :) http://zmoef.com/articles/