@Arunkumar,
doesn't work.

@Dilip,
Ok, but how can I do that? 
I add the line RETURN ApexPage.CurrentPage, but the block is not rerendered.

Public List <Account> getAccDList2() {
    List <Account> AccD =  [SELECT Id, Name, RecordTypeId, Status__c, Kunde_seit__c, Billingstreet, BillingPostalCode, BillingCity FROM Account WHERE Id = :SelectedAccountId];
    RETURN AccD;
} 

Public pageReference getAccDList() {
  getAccDList2(); 
  //RETURN NULL; 
  RETURN ApexPages.CurrentPage(); 
}

But I don't know why it not works, because I have in the same page the code below in it works fine.
Just one is different, I can use NULL this is with the code above not possible.

<div id="accList">

<apex:pageblock title="Accounts" id="pbAcc" rendered="{!IF(AccList2.size != NULL,true,false)}">
    <apex:pageblockButtons location="top">
        <apex:commandButton value="Seite 1" rerender="pbAcc" action="{!FirstPage}" disabled="{!prev}"/>
        <apex:commandButton value="vorherige Seite" rerender="pbAcc" action="{!previous}" disabled="{!prev}"/>
        <apex:commandButton value="nächste Seite" rerender="pbAcc" action="{!next}" disabled="{!nxt}"/>
        <apex:commandButton value="Letzte Seite" rerender="pbAcc" action="{!LastPage}" disabled="{!nxt}"/>
    </apex:pageblockButtons>
        <apex:pageblocktable value="{!AccList2}" var="Acc" columnswidth="5%, 70%, 15%, 10%>
            <apex:column headervalue="LINK">
                <apex:outputLink target="_blank" value="/{!Acc.Id}">Details</apex:outputLink>
            </apex:column>
            <apex:column headervalue="Accountname">
                <apex:outputField value="{!Acc.Name}" />
                <apex:actionSupport event="onclick" action="{!getOppList}" rerender="pbOpp, pbAccDL, pbAccDR, pbOppD">
                    <apex:param assignTo="{!SelectedAccountId}" value="{!Acc.Id}" name="SelectedAccountId"/>
                </apex:actionSupport>
            </apex:column>
            <apex:column headervalue="City">
                <apex:outputField value="{!Acc.BillingCity}"/>
            </apex:column>             
            <apex:column headervalue="Employees">          
                <apex:outputField value="{!Acc.NumberOfEmployees}"/>
            </apex:column>                     
        </apex:pageblocktable>   
</apex:pageBlock>

Thanks,
Sascha

Hi Sascha,

There is no need of the two methods, try something like this:

 <apex:pageBlock >
        <apex:pageBlockTable value="{!acclist}" var="acc" rendered="{!acclist.size != 0}">
            <apex:column value="{!acc.Name}"/>

        </apex:pageBlockTable>
    </apex:pageBlock>

public List<Account> acclist {get; set;}
    public vfRenderedExtension(ApexPages.StandardController controller) {
         acclist = [Select Id, Name from Account Limit 1];       
    }

There is no need of IF condition in the Rendered attribute and also no need of pageRef as well. just make sure the list is declared as property.