getting errors when I try to name a unique name.

example "What's New, url blog/news

I'm getting 404 errors... I want to change one templete, nifftypink and nifftypurple on 2 pages.... it shows that it's saved on the back in, but the page does not come up on the front-end.

and when I try to create a slug name, or url name I get the 404 error, or page not found.