Today when I visit my blog http://www.mahakumbhfestival.com/ its home page was fine but other pages were showing 404 error. I faced similar type of problem for my another blog which has very less traffic so it don’t affect much but this has special importance for me. I was unaware why I was getting 404 error for all pages even though these posts were in my database and I can view them on my WordPress dashboard. To know more on this issue I contact my web hosting provider for resolving this bug which making my website unreachable to world.
Solution to the problem
If you’re using search engine friendly URLs than you may get similar error pages. This happen because of .htaccess file which has rules for mapping website URLs to posts. If any how your .htaccess file is updated by any plugin or theme and it deleted some of its part than it may cause you similar problem. you have to again update this file by writing mapping for URLs or can ask your hosting provider for re installing this file from your website backup and you will have your website working.