I just visited Piwik on mySite.ext/piwik/ and I had these errors:

0.6.2
Warning: Cannot modify header information - headers already sent by (output started at /var/www/piwik/core/Http.php:306) in /var/www/piwik/core/Controller.php on line 403

Backtrace -->
#0 Piwik_ErrorHandler(2, Cannot modify header information - headers already sent by (output started at /var/www/piwik/core/Http.php:306), /var/www/piwik/core/Controller.php, 403, Array ([=> CoreHome,actionToRedirect => index,[=> 1,defaultPeriod => day,[defaultDate] => yesterday))
#1 header(Location:index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday) called at [/var/www/piwik/core/Controller.php:403]
#2 Piwik_Controller->redirectToIndex(CoreHome, index) called at [/var/www/piwik/plugins/CoreHome/Controller.php:41]
#3 Piwik_CoreHome_Controller->redirectToCoreHomeIndex()
#4 call_user_func_array(Array ([=> Piwik_CoreHome_Controller Object ( => CoreHome,[=> , => ,[=> 0, => ,[=> Array (label => General_ColumnLabel,[=> General_ColumnNbVisits,nb_actions => General_ColumnNbActions,[=> General_ColumnMaxActions,sum_visit_length => General_ColumnSumVisitLength,[=> General_ColumnNbUniqVisitors,nb_actions_per_visit => General_ColumnActionsPerVisit,[=> General_ColumnAvgTimeOnSite,bounce_rate => General_ColumnBounceRate,[=> General_ColumnValuePerVisit,goals_conversion_rate => General_ColumnVisitsWithConversions)),[=> redirectToCoreHomeIndex), Array ()) called at /var/www/piwik/core/FrontController.php:126
#5 Piwik_FrontController->dispatch() called at [/var/www/piwik/index.php:59]