If you don't have problem in using iCagenda, you don't have to mind of this.
iCagenda is in an intensive developpement, to add features needed.
In each update of iCagenda, i'm correcting some code, to make it better, version after version.
So, week after week, the code will evolve to be more in the last strandard of the web.
But, your none w3 validate could not only be iCagenda, but can be your site template too !
And, when iCagenda will be more developed, i will work on validation, if possible to make it W3C validated (i'm planning a ccs3 HTML5 module, so may be different)
But, if you use extensions with Joomla, you will have difficulty to have a W3C validated website.
An exemple : check
W3C validation
of
www.joomla.org ;)
