Update: This has been cleared up in HTML5 using the title attribute. Now Firefox 12 supports it. Try this:
<span title="First line Second line">Test</span>
Bad news: Firefox does not line break tooltips. This is actually a non-standard html extension, ie a bug in MSIE that may cause problem with certain pages.
See this bug on the firefox issue tracker.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…