Some times a go when I had installed my WordPress blog I was faced a issue that is the author link is not working and its giving 404 error page on clicking post author name. Its forwarding on URL some thing like the author link points to ajittiwari.com/author/ajit%20tiwari. Please see the attached screen shot for the issue.
After investigating in the data base I found that there is a space in the value of user_nickname in the wp_users table. So, if your are also facing this issue please follow following steps,
1-> Log in to your PHPMyAdmin.
2-> Select WordPress Database
3-> Select and brows wp_users table.
4-> Edit the table and put the desired URL in the user_login column
5-> Save the changes and now enjoy