[First edit, with many changes] I wanted to remove the numbering of the sections so I copied the following from this answer by user zwol:
\renewcommand{\thesection}{}
\renewcommand{\thesubsection}{\arabic{section}.\arabic{subsection}}
\makeatletter
\def\@seccntformat#1{\csname #1ignore\expandafter\endcsname\csname the#1\endcsname\quad}
\let\sectionignore\@gobbletwo
\let\latex@numberline\numberline
\def\numberline#1{\if\relax#1\relax\else\latex@numberline{#1}\fi}
\makeatother
We'll call the code above "zwol code".
I have two tex files that have the same code but where the zwol code is in different positions. We'll call "code B" to the code that has the zwol code before calling the packages. This is code B:
\documentclass[11pt, fleqn]{article}
\renewcommand{\thesection}{}
\renewcommand{\thesubsection}{\arabic{section}.\arabic{subsection}}
\makeatletter
\def\@seccntformat#1{\csname #1ignore\expandafter\endcsname\csname the#1\endcsname\quad}
\let\sectionignore\@gobbletwo
\let\latex@numberline\numberline
\def\numberline#1{\if\relax#1\relax\else\latex@numberline{#1}\fi}
\makeatother
\usepackage[vcentering]{geometry}
\geometry{papersize={3.25in,15.5in},total={3in,15in}}
\usepackage[spanish]{babel}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{graphicx}
\usepackage[utf8]{inputenc}
\begin{document}
\title{something}
\date{}
\maketitle
\section{mysection} % (fold)
\label{sec1}
lorem ipsum
\\
\end{document}
This is what I get after compiling code B with pdflatex:
And this is "code A", the code that has the zwol code after calling the packages:
\documentclass[11pt, fleqn]{article}
\usepackage[vcentering]{geometry}
\geometry{papersize={3.25in,15.5in},total={3in,15in}}
\usepackage[spanish]{babel}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{graphicx}
\usepackage[utf8]{inputenc}
\renewcommand{\thesection}{}
\renewcommand{\thesubsection}{\arabic{section}.\arabic{subsection}}
\makeatletter
\def\@seccntformat#1{\csname #1ignore\expandafter\endcsname\csname the#1\endcsname\quad}
\let\sectionignore\@gobbletwo
\let\latex@numberline\numberline
\def\numberline#1{\if\relax#1\relax\else\latex@numberline{#1}\fi}
\makeatother
\begin{document}
\title{something}
\date{}
\maketitle
\section{mysection} % (fold)
\label{sec1}
lorem ipsum
\\
\end{document}
After compiling with pdflatex:
When I compile code B with pdflatex, the pdf showed dots before the section titles: ". mysection". However, with code A, the pdf appeared as I wanted it, showing the sections titles without any dot before them: "mysection" .
Why did this happen?


\addtolengthcommands in order to see a section title. – egreg Apr 10 '18 at 21:06multicolis added with a quite large\columnsep. This gives very narrow columns. – Heiko Oberdiek Apr 10 '18 at 21:08dvipson the line with thegeometrypackage. Most probably I just copy-pasted that from somewhere. Do you think that line of code may be related to the problem? Keep in mind that I was compiling my tex file with pdflatex on a MacBook's Terminal – evaristegd Apr 10 '18 at 21:58geometrycan not set the pdf page size at all, but impossible to say anything about your problem as you have posted no test code. – David Carlisle Apr 10 '18 at 22:05