By default LaTeX starts the footnote counter at zero for each chapter when you use the class {book} or {scrbook}. If you want to avoid that and have a continuous enumeration, here is how it works:
Create a folder <remreset> in your local package repository. Save the file remreset.sty into this folder.
Open your preamble and add
\@removefromreset{footnote}{chapter}
Should you get an error message like this
or like this
embrace the stuff with \makeatletter and \makeatother:
\makeatletter
\@removefromreset{footnote}{chapter}
\makeatother
Voilà.