htdocs”, “html”, “public” or “httpdocs”. Not Found

Hello i try to install Google xml sitemap plugin and says

There was a problem writing your sitemap file. Make sure the file exists and is writable. Learn more

You can make your whole blog root folder writable and the plugin will create the files for you. You can do this by using a FTP program and setting CHMOD to 755 or 777 to your web-root folder. This folder is often named “htdocs”, “html”, “public” or “httpdocs”.

The Problem is i can’t find those files
htdocs”, “html” “public” or “httpdocs

by defult must be on my blog root?

Please give me some solution for that
Thanks in advance