<apex:page controller="regioncontroller" sidebar="false" showHeader="false" standardStylesheets="true" >
<style>
    .outergridvalidationcolumn {
        padding: 0px 30px 10px 0px;
    }
</style>

<apex:sectionHeader title="Action Region Demos"/>    
<apex:outputPanel style="max-width:30%;" layout="block">
<apex:pageBlock >
    <apex:form >
        <apex:pageMessages id="messagesForm1"/>    
        <apex:pageBlockSection columns="2" title="WITHOUT Action Region">
            <apex:outputText value="Name" />
            <apex:inputText value="{!name}">
                <apex:actionSupport event="onkeyup" reRender="outname,messagesForm1" />
            </apex:inputText>
            <apex:outputText value="Job" />
            <apex:inputText required="true" id="job2" value="{!job}" />
        </apex:pageBlockSection>
    </apex:form>
    
    <apex:form >
        <apex:pageMessages id="messagesForm2"/>    
        <apex:pageBlockSection columns="2" title="WITH Action Region">
            <apex:outputText value="Name" />
            <apex:actionRegion >
                <apex:inputText value="{!name}">
                    <apex:actionSupport event="onkeyup" reRender="outname,messagesForm2" />
                </apex:inputText>
            </apex:actionRegion>
            <apex:outputText value="Job" />
            <apex:inputText required="true" id="job1"  value="{!job}" />
        </apex:pageBlockSection>
    
        <apex:outputText id="outname" style="font-weight:bold" value="Typed Name: {!name}" />
    
    </apex:form>    
</apex:pageBlock>
</apex:outputPanel>
</apex:page>

http://www.tgerm.com/2010/09/visualforce-actionregion-deep-dive.html

Visualforce Page for ActionRegion Demo

XML