achellios

WordPress bloggers will sometimes copy headlines from a WordPress-generated homepage and paste them into the post-editing window. In Firefox, this has the unfortunate result of converting absolute urls into relative ones. For example, copying a headline from http://khaotica.com converts the permalink for this article:
http://khaotica.com/2009/12/firefox-relative-links-fix-wordpress.html
…to a relative link:
../2009/12/firefox-relative-links-fix-wordpress.html
This creates broken links when the post is viewed on the archive page and RSS feed. The links will also be broken for subscribers who receive posts via email.
Enter the Relative Links Fix. This plugin will replace relative urls with the proper absolute urls every time you save or publish a post. If you use WordPress and can’t shake those copy-paste habits, this is the plugin for you.
As always, donations are appreciated. I promise to spend them exclusively on soda (the creative fuel that powers developers everywhere).

Relative Links Fix

Corrects Firefox behavior in which pasting formatted content in the editor converts absolute URLs to relative URLs.

Semio Design

Pierre-André Boissinot

When you use the WordPress editor to insert a media in the content field it stores a reference to the absolute path. 
So if you change the location of your site (by switching from staging to production environment for example) all your paths will be incorrect. 
This plugin stores relative pathes in the db instead of an absolute path. 
Beware: this plugin must be activated BEFORE inserting a media into the content field. It has no effect on the medias stored before the activation. 
It’s mostly based on the WP_SITEURL constant which should be defined in the wp_config.php file. If this constant isn’t defined it uses the “siteurl” option value instead. 
If the plugin detects that you access the website from another location than the “siteurl” defined initially it can correct most of the wrong urls in the database.
Localisation of the plugin into french.

Simple Relative Content

This plugin makes all attachments urls stored in database relative to the WP_SITEURL url.

Relative Links Fix vs Simple Relative Content