The text “height” keeps popping up in tables

Question

In my LaTeX document, I have some simple code for the simplest of tables. But, when I let TeXnicCenter output it to PDF, the text 'height' is suddenly in the first cell and on the first cell in a new row I didn't define. Of course googling for the height and table gives lots of results, but not to this question

\begin{table}[h]
    \begin{tabular}{|l|l|l|l|l|}
        \hline
        ~ & $\theta$      & d   & a  & $\alpha$ \\ \hline
        1 & 0             & 100 & 0  & $\pi$    \\ 
        2 & 0             & 0   & 90 & 0        \\ 
        3 & $\frac{\pi}{2}$ & 50  & 0  & 0      \\
        \hline
    \end{tabular}
\end{table}

Answer 1

It seems that you must have something like the following in your code, where you have height instead of \hline:

\documentclass{article}
\begin{document}
\begin{table}[h]
    \begin{tabular}{|l|l|l|l|l|}
        height
        ~ & $\theta$      & d   & a  & $\alpha$ \\ \hline
        1 & 0             & 100 & 0  & $\pi$    \\ 
        2 & 0             & 0   & 90 & 0        \\ 
        3 & $\frac{\pi}{2}$ & 50  & 0  & 0      \\
        height
    \end{tabular}
\end{table}
\end{document}

The above produces the output you provided. With height in the above replaced with \hline (as per your MWE), I get the following. So, your MWE is correct, but check your actual code.