<p> This is a paragraph with a standard line-height. The default line height in most browsers is about 110% to 120%. This is a paragraph with a standard line-height. This is a paragraph with a standard line-height. </p>
<p class="small"> This is a paragraph with a smaller line-height. This is a paragraph with a smaller line-height. This is a paragraph with a smaller line-height. This is a paragraph with a smaller line-height. </p>
<p class="big"> This is a paragraph with a bigger line-height. This is a paragraph with a bigger line-height. This is a paragraph with a bigger line-height. This is a paragraph with a bigger line-height. </p>
Microsoft Internet Explorer 3.x incorrectly treats number values and values with em or ex units as pixel values. This bug can easily make pages unreadable, and so authors should avoid provoking it wherever possible; pixels units are often a good choice.
For some reason, Opera 4 will 'inherit' inline absolute (as well as pixels) line height declarations back up to the previous line. Thus if you specify line-height: 200px on an inline element, it will also affect text on the previous and following lines.
Not sure who still uses IE 3 and Opera 4 they are really really really old:-).