I then began to play around with permalink structures
I think the error is something to do with me writing a custom permalink: from default to /index.php/%year%/%monthnum%/%day%/%postname%/. This then give me the the 404 error stating that wp-login.php was not found on this server!
I try to find the answer with google, and i found the article to solved my problem,here i give the resolved if you don’t want to read the article.
If you have access to the site via FTP, then this method will help you quickly get a site back up and running, if you changed those values incorrectly.
1. FTP to the site, and get a copy of the active theme’s functions.php file. You’re going to edit it in a simple text editor (like notepad) and upload it back to the site.
2. Add these two lines to the file, immediately after the initial “<?php” line.
Use your own URL instead of example.com, obviously.
3. Upload the file back to your site, in the same location. FileZilla offers a handy “edit file” function to do all of the above rapidly, if you can use that, do so.
4. Load the login or admin page a couple of times. The site should come back up.
5. Repeat the above steps, but remove those lines. IMPORTANT: Do NOT leave those lines in there. Remove them immediately after the site is up and running again.
If there is no functions.php file in the theme: Create a new text file called “functions.php”. Edit it with notepad, and add this text to it, using your own URL instead of example.com:
<?php update_option('siteurl','http://example.com/blog'); update_option('home','http://example.com/blog');
Upload that to your theme directory, then proceed as stated above. Remove the file afterwards.
and then i can resolved my problem and my site running again normally.