When compiling the code, I did not throw any errors on the line indicated in the comment (63). Anyway to avoid any error with that double horizontal line, it is preferable to just leave a \hline . Also, I made a couple of changes in its code to center the titles and put them in negrita , plus some format corrections and other minor ones that I will explain below.
\documentclass[12pt, a4paper]{article}
\usepackage[utf8x]{inputenc}
\usepackage{xcolor}
\usepackage{graphicx}
\usepackage{lipsum}
\colorlet{LIME GREEN}{green}
\renewcommand{\figurename}{Figura}
\title{\textbf{\textcolor{green}{Tipo de vulnerabilidad \
\large SPF BAD CONFIGURATION }}}
\author{}
\date{}
\begin{document}
\maketitle
\noindent El protocolo SPF (Sender Policy Framework) es un protocolo empleado para...
\lipsum[1]
\begin{figure}[ht]
\includegraphics[width=\linewidth]{funcionamientoSPF}
\centering
\caption{Funcionamiento de SPF}
\end{figure}
\lipsum[2]
\begin{table}[htbp]
\centering
\begin{tabular}{|c|p{10cm}|}
\hline
\textbf{Opción} & \multicolumn{1}{c|}{\textbf{Descripción}} \ \hline\hline
\verb|+all| & Indica que se autoriza el envío de correo desde servidores no declarados en el registro \ \hline
\verb|~all| & Indica que se autoriza el envío de correo desde servidores no declarados en el registro SPF, recomendando los declarados en el mismo. Es probable que entre como spam si el rango no está bien definido \ \hline
\verb|-all| & Indica que no se autoriza explícitamente el envío de correo desde servidores no declarados en el registro SPF \ \hline
\verb|?all| & "No se puede decir nada de la validación", el correo es aceptado \ \hline
\end{tabular}
\end{table}
\bigskip
Un registro SPF cuidadosamente diseñado reducirá la probabilidad de que el nombre de domicilio se falsifique y evite que los mensajes se marquen como spam antes de que lleguen a sus destinatarios.
\end{document}
Changes made:
For practical reasons, I deleted the packages that were superfluous for the purpose of the response in order to minimize the code and simplify.
I added \usepackage[utf8x]{inputenc} , which is the package for accents and characters as ñ in Spanish, which does not require the babel package. As you can see in the code, all the words are accentuated without problem, in addition to the separation of them is given according to the rules of the Castilian language.
I also added \author{} and \date{} , because I originated an error with the date on the one hand, and on the other, I did not see necessary to indicate the name of the author. It will remain at your discretion.
The \renewcommand{\figurename}{Figura} instruction in the preamble is to change the title of the figures in the figure environment, since by default it is in English.
With respect to the table, I put it in the% table environment, which is a floating figure that can be handled between the text of the page. The [htbp] parameter is always recommended.
As you can see the table use \multicolumn{}{}{} which in this case works to center only that cell of the title.
I centered the first column and put the commands "all" between \verb| | to leave it in verbatim , very usual typographically when it comes to writing "raw" commands.
The correct use of quotes is '' texto'' instead of enclosing it in the typical "texto" .
I also made other minor corrections in some words that had errors.
On the other hand, there are other observations that I allow myself to make about the presentation of the tables (according to the typographical conventions), among others. And I must clarify that this is already an optional issue: as an extended recommendation in the world of typography, it is usually avoided at all costs the use of vertical lines in the tables. Whether for stylistic or format issues, it is recommended to dispense with them. This use is the one that by convention has been taken now in the texts that contain these elements, and it can not be denied that this simplicity gives a very aesthetic character to the text. Here is the code of your table with these changes.
\begin{table}[htbp]
\centering
\begin{tabular}{cp{10cm}}
\toprule
\textbf{Opción} & \multicolumn{1}{c}{\textbf{Descripción}} \ \midrule
\verb|+all| & Indica que se autoriza el envío de correo desde servidores no declarados en el registro \[1ex]
\verb|~all| & Indica que se autoriza el envío de correo desde servidores no declarados en el registro SPF, recomendando los declarados en el mismo. Es probable que entre como spam si el rango no está bien definido \[1ex]
\verb|-all| & Indica que no se autoriza explícitamente el envío de correo desde servidores no declarados en el registro SPF \[1ex]
\verb|?all| & ''No se puede decir nada de la validación'', el correo es aceptado \[1ex] \bottomrule
\end{tabular}
\end{table}
P.D : It is NOT recommended to color the titles.