Error 520: Web server is returning an unknown error

widget('zii.widgets.CMenu',array( 'items'=>array( array('label'=>'Home', 'url'=>array('/site/index'),/*'visible'=>!Yii::app()->user->isGuest*/), array('label'=>'Master','url'=>array('/site/master'),'visible'=>Yii::app()->user->isAdmin()), array('label'=>'Transaction','url'=>array('/site/transaction'),'visible'=>Yii::app()->user->isAdmin()), array('label'=>' Alotted Task','url'=>array('/site/alottedtask'),'visible'=>!Yii::app()->user->isGuest), array('label'=>'Completed Task','url'=>array('/site/completedtask'),'visible'=>!Yii::app()->user->isGuest), array('label'=>'Status Update', 'url'=>array('/site/statusupdate'),'visible'=>Yii::app()->user->isAdmin()), array('label'=>'Login', 'url'=>array('/site/login'), 'visible'=>Yii::app()->user->isGuest), array('label'=>'Logout ('.Yii::app()->user->name.')', 'url'=>array('/site/logout'), 'visible'=>!Yii::app()->user->isGuest) ), )); ?>