Partial TextString Property Editor for Umbraco
This is a small extension to a standard "Textbox" editor, that allows you to specify a prefix and/or suffix string to show alongside the editor.
Sometimes that's much better than trying to use the description to explain that you should only type in e.g. the username for an email account or similar.
This package should work in both Umbraco 7 and Umbraco 8.