Many people (bloggers) are talking about the problem of wp-admin.php page which is not opening when they are trying to reach it.It is giving error 404 page not found.I had also this error but i was able to resolve it by following these steps:

Go to your ftp software mine is flashfxp

Login to your website

Take a back up of your whole website

Now go to top folder’s i.e  wp-admin,wpau-backup,wp-content,wp-includes Check their attribute status It might be converted to 757 and files attribute might be 646 which should be 755 and 644 for default.

Change All folders to 755 and all files to 644

Reminding you i am saying about all go through each folder inside your blog there are many of them and try no one is left .

Change also the attribute of all of your files which are outside of these folders like wp-app.php,wp-atom.php etc.

Do it to all

That’s it