the borders of the colored cells disappear in low size and appear when zooming in. Here is my code
\documentclass[12pt, fleqn]{article}
\usepackage[portuges]{babel}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{colortbl}
\usepackage{hhline}
\begin{document}
\begin{table}[ht]
\centering
\begin{tabular}{|c|c|c|c|c|}
\hline
\rowcolor[gray]{0.8} A & B & C & D & E\\
& & & number1 & number2\\\hline
10 & 20 & 30 & 20 & 10\\
& & 15 & & 8\\\hline
\end{tabular}
\caption{}
\end{table}
\end{document}
I want the upper horizontal line to appear. But the result is as shown here..

i know it is a duplicate question how to prevent cell color to cover table's borders?, but the solutions provided didn't solve my problem.
\hlineinstead of\clineand still the same result."the upper border disappear" – Fadwa Mar 04 '14 at 13:27\setlength{\arrayrulewidth}{2pt}to increase the thickness of rules in a table. – Jesse Mar 04 '14 at 13:53%at ends of lines. – David Carlisle Mar 04 '14 at 15:16