[SalesForce] ContentVersion: how to check File Type and File Size

<apex:inputCheckbox value="{!attached.check}">
  <apex:actionSupport event="onchange" action="{!calculateTotalFileSize}">
     <apex:param name="attachmentID" value="{!attached.att.Id}"
                            assignTo="{!selectedAttachmentId}"/>
    </apex:actionSupport>
</apex:inputCheckbox>

public pageRefrence calculateTotalFileSize(){
    // do your addition and subtraction based on condition
}

remove the Body field from SOQL Query,

Query Like this:

for(Attachment a : [Select Id, BodyLength, Name, Description, ParentId, ContentType 
                    From Attachment 
                    Where ParentId = :cases.Id 
                    And BodyLength < :value])

I faced this now too and after ....

1. adding the guest user to a public group
2. creating a public library and then adding the file to that library

If I use

<img style="max-width: 100%;" src="/sfc/servlet.shepherd/version/renditionDownload?rendition=THUMB720BY480&versionId={!ContentVersionId}"/> 

it doesn't work but if I use

<img style="max-width: 100%;" src="https://XXXX--YYYY--c.INSTANCE.content.force.com/sfc/servlet.shepherd/version/renditionDownload?rendition=THUMB720BY480&versionId={!ContentVersionId}"/>

then it works.

Compare your /apex version of the visualforce (right click on the image and open link) with the site.com URL and you will see there's a small difference.