unmarked footnote

\documentclass{article}
\usepackage{lipsum}

\newcommand\blfootnote[1]{%
  \begingroup
  \renewcommand\thefootnote{}\footnote{#1}%
  \addtocounter{footnote}{-1}%
  \endgroup
}

\begin{document}

Some text\blfootnote{A footnote without marker} and some more text\footnote{A standard footnote}

\end{document}