To add hard spaces in your pages you could use " ", but after problems with this HTML command on Mac OS X (and the parsing methods of XML::Simple), I have decided to add an alternative:
{{{SPACE:42}}}
The number 42 in the example above is only a place holder for any number you like. In that example Spip would insert 42 times " " at the position of the SPACE command.
For example I inserted {{{SPACE:4}}} in front of the line with the SPACE command above, to create some space in front of it.