Extension Contraller

<apex:page standardController="Account"
extensions="ExtOne,ExtTwo">
<apex:outputText value="{!foo}"
/>
</apex:page>

public class ExtOne {
private ApexPages.StandardController
sdController;
public ExtOne(ApexPages.StandardController acon) {sdController
= acon; }
public String getFoo() {
return 'foo-One';
}
}

public class ExtTwo {
private ApexPages.StandardController
sdController;
public ExtTwo(ApexPages.StandardController acon) {sdController
= acon; }
public String getFoo() {
return
'foo-Two';
}
}