The placeholder attribute for <input> and <textarea> is supported on Firefox3.7/Chrome/Safari. Placeholder text is displayed when text is empty and is not focused. It is very easy to use:

<input type="text" placeholder="empty text" value="">
<textarea placeholder="empty text">

When placeholder="foo&#x0a;bar" is specified to <textarea>, "&#x0a;"(LF) is removed on Firefox. On Chrome, line break after "foo".

Since HTML 5 specification deny "&#x0a;"(LF) to placeholder attribute, it seems to be no matter. "&#x0a;"(LF) MUST NOT be contained in placeholder attribute. (i.e. placeholder must be a single-line text)

The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.