Now you can use the lovely HTML5 'placeholder' attribute and have it work 'everywhere'. This module integrates the HTML5 Placeholder jQuery Plugin found here:
https://github.com/mathiasbynens/jquery-placeholder
with Drupal. This is a javascript-only method of making the HTML5 placeholder attribute work in old browsers which don't support it.
Note: The latest version of this plugin requires jQuery 1.6+. For an older version that works under jQuery 1.4.2+ (which Drupal 7 includes by default) see v1.8.7.
(It should also work with any other jQuery plugin which is called in the same way - e.g. https://github.com/danielstocks/jQuery-Placeholder)
Installation
1. Download the jQuery placeholder plugin of your choice to, e.g., sites/all/libraries/jquery.placeholder
2. Install the Elements module
3. Use the '#placeholder' attribute on form elements!
Usage
It should JustWork with the Elements module, allowing you to use placeholders on your form elements as follows:
$form['mytextfield'] = array(
'#type' => 'textfield',
'#title' => t('My example textfield'),
'#placeholder' => t('Please enter a value'),
);