Tweaking the CSS

sIFR-screen.css, contains several default rules for h1 to h5 elements that help to determine
the dimensions of the Flash replacements. In order to understand how you should use
these rules, you need to understand how sIFR does its job and how fonts relate to one
another.
You can see in Figure 1.14 that the Flash replacement and the HTML text are different
lengths when displayed side by side. This discrepancy arises as a result of the fact that
the font used in the Flash replacement differs from that used in the HTML, and because
different fonts have different character metrics (including width, spacing, and so on).
This difference in length becomes a particular problem when a line of text starts to wrap
onto the next line. If the HTML text isn’t wrapping but the Flash text is, sIFR will shrink
the size of the Flash text so that it fits onto one line. This means that the size of the Flash
replacement may be inconsistent, depending upon the number of characters in the HTML
text. Conversely, if the HTML text is wrapping when the Flash text