Unterstreichen

underbar

The macro \underbar cannot have linebreaks. It's better to use one of the packages ulem or soul. For the ulem-package write in LatEX-preamble:

\usepackage{ulem}
		\let\underbar\uline
		\let\underline\uline

from the ulem package:

%  Full instructions appear after \endinput.  In summary:
%    \uline{important}   underlined text
%    \uuline{urgent}     double-underlined text
%    \uwave{boat}        wavy underline
%    \sout{wrong}        line drawn through word
%    \xout{removed}      marked over with //////.
%    {\em phasized\/}  | In LaTeX, by default, these are underlined; use
%    \emph{asized}     | \normalem or [normalem] to restore italics
%    \useunder{\uwave}{\bfseries}{\textbf}
%                        use wavy underline in place of bold face

Dashed or dotted underline

The following code defines the macros

\usepackage{ulem}
\def\dotuline{\bgroup
  \ifdim\ULdepth=\maxdimen  % Set depth based on font, if not set already
    \settodepth\ULdepth{(j}\advance\ULdepth.4pt\fi
  \markoverwith{\begingroup
  \advance\ULdepth0.08ex
  \lower\ULdepth\hbox{\kern.15em .\kern.1em}%
  \endgroup}\ULon}

\def\dashuline{\bgroup
  \ifdim\ULdepth=\maxdimen  % Set depth based on font, if not set already
    \settodepth\ULdepth{(j}\advance\ULdepth.4pt\fi
  \markoverwith{\kern.15em
  \vtop{\kern\ULdepth \hrule width .3em}%
  \kern.15em}\ULon}

Quelle: http://www.tug.org/TeXnik/mainFAQ.cgi?file=misc/underline