Assume that you type a page name, such as “Text with space” in the New item form in a pages library in SharePoint Server 2013 to create a new page. After you create the page, the automatically generated URL is inconsistent with the preview URL. For example, the preview URL may be displayed in a label as follows:
1. Go to "Site Settings".
2. Click on "Page Layout and Site Template Settings" under "Look and Feel".
3. Scroll down and check option "Convert blank spaces in page name to'-'".
If you have installed SharePoint April to September Cumulative Update package 2015 then you might face above error even you have checked the option given in solution above.
This issue is resolved in October 2015 Cumulative Update. Reference Links are: