In order to copy the file index.html from the local machine to vesuri.helsinki.fi the following command is needed:

scp -p /Volumes/Documents/michael/Sites/index.html mjeltsch@vesuri.helsinki.fi:./public_html/index.html

The full path of the original file (/Volumes/Documents/michael/Sites/index.html) is of course not needed if the file is in the current directory.