The Microsoft HTML Help viewer, which is based on Internet Explorer, supports CSS (cascading style sheets); however, not every CSS feature is supported. Although CSS is probably the best way to set display properties for HTML Help, you might have to experiment. If a CSS feature you try does not seem to work, check the HTML Help Workshop on-line Help, or check with Microsoft to make sure HTML Help supports that feature.
For on-demand font resizing via the Font button (see §8.3.3 ), CSS font sizes must be in relative units: em, ex, or %. For best practice, use em. By default, Mif2Go generates CSS entries using absolute pt units for font size and line height. To change the units, see §21.8.3 .