\documentclass{article}

\usepackage{booktabs}

\begin{document}

% HTML looks like \cmidrule{1-3} was used.
\begin{tabular}{llllll} \toprule
  a & b & a & b & a & b \\ \cmidrule{2-3}
  c & d & c & d & c & d \\ \bottomrule
\end{tabular}

% HTML has three separate `rules' in separate tr elements.
\begin{tabular}{llllll} \toprule
  a & b & a & b & a & b \\ \cmidrule{2-2} \cmidrule{3-4} \cmidrule{6-6}
  c & d & c & d & c & d \\ \bottomrule
\end{tabular}

\end{document}
