Section C.2 explains how to configure a few browsers to get the right symbols. In that case replacement text is in French. This is far from being satisfactory, but degraded mode may be appropriate for documents than contain few symbols. For instance, fractions numerators and denominators must be placed one above the other. Text mode is the mode for typesetting normal text, when in this mode, text items are echoed one following the other and paragraph breaks are just blank lines, both in input and output.
Displays come in two flavor, horizontal displays and vertical displays.
These tables holds display elements, displays elements being centered vertically in horizontal display mode and horizontally in vertical display mode. The distinction between text and display modes clearly appears while typesetting math formulas. Thus, some formulas may be rendered poorly. For instance, two fractions with different denominator and numerator height look strange. Such a crude model cannot faithfully emulate any TeX box placement.