How to Change Deprecated Tags in WordPress

1. Download your website's wp-config.php file to your computer and open it in a code editor or Notepad. Find the following code at around line 81 of the file:define('WP_DEBUG', false);Change 'false' to 'true' and save the file. Upload it to your server and overwrite the current copy of your configuration file.
2. Load your website in a browser to see errors and warning messages. WordPress prints messages about deprecated tags wherever it finds them, so look over your entire website to find them all. Each warning includes a suggested replacement for the deprecated tag plus information about where to find the old code. Copy and paste that information into a blank text file so you can read it while you edit your code.

3. Download all the files for your theme to your computer and open them in a code editor or Notepad. Open your editor's 'Replace' tool and type the name of your first deprecated tag into the 'Find' field. Type the new code, as suggested by the warning message, into the 'Replace' field. Click 'Find Next' to find the tag in a template and click 'Replace' when you find the tag. Do this for every deprecated tag on one template file and then move on to the next template file. Note that you need only to check your PHP files.
4. Save your theme files and upload them to your server, overwriting the old version of the theme. Reload your website in the browser and look again for any deprecated tag warnings. As long as you fixed all your tags, you should not find any more warnings.