After reading (and reading ...) it is not 100% clear to me how this should be done.

For example:

Force a click on a link to be recorded as a download in Piwik

If you want Piwik to consider a given link as a download, you can add the piwik_download css class to the link:

<a href='last.php' class=piwik_download>Link I want to track as a download</a>

Note: you can customize and rename the CSS class used to force a click to being recorded as a download:

[...]
// now all clicks on links with the css class download will be counted as downloads
piwikTracker.setDownloadClass( download );
piwikTracker.trackPageView();
[...]

Once you are talking of 'piwik_download', then of 'download'.
Does this mean that Piwik recognize the CSS.class 'piwik_download' as 'download' and records it?
Or is this only a type and it should be always 'piwik_download' or 'downlaod'.

And - must it be always (piwik_)download or can i name the css.class as i want?
Therefore i have to build up the piwik js.code with this won created css.class

I am only asking, because i am building some implementations and widgets dynamically.

Thanks
michael