Visualforce inputfield for lookup not displaying clear icon

Question

I've added a custom field to the Case standard object which is a lookup to Account, named Site__c

When I create a visualforce page to allow for editing of the Site__c and Account fields on a Case, they are rendered slightly differently. The (Standard) Account field has a clear button and the text input is disabled, but i can't get the Site__c field to match.

How can I achieve this? ![example] https://i.sstatic.net/aD7r1.jpg

VF:

    <apex:inputField id="Customer" label="Account" value="{!caseRec.AccountId}" style="width: 75%;" >
        <apex:actionSupport event="onblur" 
            action="{!assignAccountId}" 
            rerender="pbSection,pgButtons,PageBlock,caseProfile" />
    </apex:inputField>
    <apex:inputField id="Site" label="Site" value="{!caseRec.Site__c}" style="width: 75%;" >
        <apex:actionSupport event="onchange" 
            action="{!selectmethodSite}" status="loadStatus"
            rerender="pbSection,msg,caseProfile"/>
    </apex:inputField>

Answer 1

The clear button near Account shows that the field is part of lookup filter.

If you want your custom lookup to have the same clear button, your custom lookup should be part of any lookup filter.

Lookup filter documentation

Hope it helps.