Code: Select all
\documentclass[a4paper,11pt]{article}
\usepackage{colortbl}
\begin{document}
\begin{tabular*}{\textwidth}[H]{@{\extracolsep{\fill}}|l|c|c|}
\hline
& \multicolumn{2}{c|}{} \\
& & \\ \hline
\multicolumn{3}{|l|}{} \\ \hline
& \cellcolor[gray]{0.85} &\cellcolor[gray]{0.85} \\ \hline
\end{tabular*}
\end{document}
EDIT: I solved my problem by switching to the tabularx environment, which provides a more sane way of stretching tables - namely, by stretching the columns and not increasing the intercellular space (as done by tabular*).