Wordpress Plugins
HTML Tag and Class Replacer for WordPress
Knowing a little bit of PHP, HTML, and CSS goes a long way towards helping you customize your WordPress site faster. You can always come up with a SQL command to make changes to your content. It is also possible to do it manually from the back-end.. Plugins such as HTML Tag and Class Replace are also worth a look. It lets you replace any HTML tag.
This plugin can not only replace HTML tags but also class names. Before using plugins like this, you will want to back up your database. Plugins like this are much safer than trying SQL updates if you are an expert in that language. It can handle header, body and footer sections.