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<apex:page ><apex:page sidebar="false"> <!--Flight Systems Checklist Visualforce Page--> <h1>Checklist</h1> <apex:form id="engineReadinessChecklist"> <apex:pageBlock title="Flight Systems Checklist"> <!--First Section--> <apex:pageBlockSection title="Engines"> <!--Adding Checkboxes--> <apex:inputCheckbox immediate="true"/>Engine 1 <apex:inputCheckbox immediate="true"/>Engine 2 <apex:inputCheckbox immediate="true"/>Engine 3 <apex:inputCheckbox immediate="true"/>Engine 4 <apex:inputCheckbox immediate="true"/>Engine 5 <apex:inputCheckbox immediate="true"/>Engine 6 </apex:pageBlockSection> <!--Second Section--> <apex:pageBlockSection title="Fuel Tanks"> <apex:inputCheckbox immediate="true"/>Tank 1 <apex:inputCheckbox immediate="true"/>Tank 2 <apex:inputCheckbox immediate="true"/>Tank 3 <apex:inputCheckbox immediate="true"/>Tank 4 <apex:inputCheckbox immediate="true"/>Tank 5 <apex:inputCheckbox immediate="true"/>Tank 6 </apex:pageBlockSection> <apex:pageBlockButtons> <!--Adding Save Button--> <apex:commandButton value="Save" action="{!save}"/> </apex:pageBlockButtons> </apex:pageBlock> </apex:form> </apex:page> </apex:page> Cyclic page or component references '/apex/FlightSystemsChecklist' are not allowed
To start, a VisualForce Page can only have ONE root <apex:page></apex:page> element. Your code has two. Right at the beginning you have
<apex:page >
<apex:page sidebar="false">
........
</apex:page>
</apex:page>
Remove the outer tags and that should correct this issue.
You also have the code
<apex:commandButton value="Save" action="{!save}"/>but there is no standard controller or custom Apex controller in your code.
If this is for a Trailhead module. Remove the outer tags and resubmit. You may get more specific guidance as to how to correct this.
If this is not for Trailhead and you need a standard controller, your first line should look something like:
<apex:page standardController="Account" sidebar="false">
(You can replace "Account" with whatever object you are using)
Also, your checkboxes aren't bound to fields or variables. Not sure whether this is intentional. I would expect them to look more like:
<apex:inputCheckbox value="{!Account.My_Field_Name__c}" />If you need something more custom, please explain more about what you are trying to accomplish.
