tex4ht with computer modern.tex

\documentclass{article}

\usepackage[T1]{fontenc} % sets font encoding
\usepackage{lipsum}
\usepackage{url}
\usepackage{enumitem}
\newlist{floatnotes}{description}{1}
\setlist[floatnotes]{before=\footnotesize}

\usepackage[
  font=small,
  indentfirst=false,
  rightmargin=.5\leftmargin,
  ]{quoting}

\title{A Title}
\author{Author\thanks{Some thanks here.}}

\begin{document}

\maketitle

\begin{abstract}
Abstract seems smaller than \verb|\small|.
\lipsum[2]
\end{abstract}

\lipsum[1]\footnote{A footnote here. Footnotes same size as normal text (I'm not
  sure this is not what is intended.).}

Urls look big: \url{http://www.google.com}.

\begin{floatnotes}
\item[Obs.:] A custom environment set to \verb|\footnotesize|, looks much smaller than the
  footnotes.
\item[Obs. 2:] Paragraph breaks are not respected inside description environment
  or relative to previous paragraph.
\item[Notes:] \lipsum[3]
\end{floatnotes}

\end{document}
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