ActionStatus in salesforce

---- visual force----
<apex:page controller="actionstatuscontroller">
    <apex:form >
        <apex:pageBlock id="pbid" >
            <apex:pageBlockTable value="{!insertval}" var="ins" rendered="{!dsf}">
                <apex:column value="{!ins.id}"/>
                <apex:column value="{!ins.name}"/>
            </apex:pageBlockTable>
            <apex:actionStatus id="actionstatusid">
                <apex:facet name="start">
                <apex:image url="{!$Resource.loading}" /></apex:facet>
            </apex:actionStatus>
            <apex:commandButton value="Display Records" action="{!display}" status="actionstatusid" reRender="pbid"/>
        </apex:pageBlock>
    </apex:form>
</apex:page>

----- Controllers ----

public class actionstatuscontroller {

    public Boolean dsf { get; set; }

    public Boolean getDsf() {
        return null;
    }
    public PageReference display() {
     insertval =[select id,name from account];
     dsf=true;
        return null;
    }


    public List<Account> insertval { get; set; }

    public List<Account> getInsertval() {
        return null;
    }
   
}