> So, when i'm making
> 
>       <xsl:if test="$main">
> 
> what am i saying in english?
> 

You are saying: when I convert the value of $main to a boolean, is the
result true?

The values that convert to false (in 1.0) are the boolean false(), the
number 0, a zero-length string, and an empty node-set. Everything else
converts to true.

When you specify a stylesheet parameter like this:

   <xsl:param name="p"/>

then the default value (if the caller supplies no value) is a zero length
string.

Michael Kay
http://www.saxonica.com/