RaymondDesign

When you want to place a small text rule, an advertisement or something else at the top or bottom of your post or page, it is possible to edit your theme. But you lose all your changes when you update you theme. 
With Post & Page Notes, shortly PPNotes you can put your own text or image on a post or page, without editing your theme. So, when you update your theme or something else the Post & Page Notes are kept.
When you have installed this plugin, you have two forms, one for the header text and one for the footer text. For every form (header and footer), you can set where you want to show the text. You can choose from a list: ‘Post’, ‘Page’ and ‘Post & Page’. If you choose ‘Post’ the header or footer is visible at every single post, if you choose ‘Page’ the header or footer is visible on every page (except the pages with single posts and the archives). If you choose ‘Page & Post’ the header or footer is visible on both single posts and pages.
In the text fields, you can type plain text or (x)HTML, so it’s possible to place (nice styled) div’s or images at the top of your posts or pages.

Post & Page Notes

Post & Page Notes, shortly PPNotes is a plugin to simply at a header and footer to your posts and pages, without editing your theme.

Mark

Adds a simple ‘Post-it’ widget to the Dashboard that allows you to leave yourself or other authors a note. The plugin can be configured and moved around as any other Dashboard widget. It will accept plain text or (sanitized) HTML. Only users with the capability “Edit dashboard” can edit the note.
This simple plugin is based on code from <a href="http://wpengineer.com/add-wordpress-dashboard-widgets/" title="Add WordPress Dashboard widgets" rel="nofollow ugc">WP Engineer</a> and <a href="http://rick.jinlabs.com/2009/02/01/how-add-options-to-your-wordpress-27-dashboard-widgets/" title="How to add options to your WordPress 2.7 Dashboard widgets" rel="nofollow ugc">Ricardo González Castro</a>. Leave your comments <a href="http://ideophone.org/dashboard-post-it/" title="Dashboard Post-it homepage" rel="nofollow ugc">here</a>.
Warning Your notes will be replaced by boilerplate text upon upgrading. Make sure to copy the content somewhere else before you upgrade and then paste it into the new version. Sorry about that!

Dashboard Post-it

Adds a simple 'Post-it' widget to the Dashboard that allows you to leave yourself or other authors a note.

Post & Page Notes vs Dashboard Post-it