* <a href="http://www.w3.org/TR/CSS21/syndata.html#length-units">Lengths</a>
* require units unless the value is zero. All browsers assume px if the
* suffix is missing.
*/
private void fixTerms(AncestorChain<? extends CssTree> t) {
SymbolInfo stdColors = cssSchema.getSymbol(Name.css("color-standard"));
final Pattern stdColorMatcher;
if (stdColors != null) {
stdColorMatcher = new CssPropertyPatterns(cssSchema)
.cssPropertyToJavaRegex(stdColors.sig);
} else {