Update, for version 11.0 Enterprise:

1. Create new model.

2. Menu with Window Action: Target Window: Inline Edit; View Mode: Form. Tree

3. Form View:

<?xml version="1.0"?> 

 <form string="Embedded Webpage" version="7.0" edit="false" create="false"> 

<center>

 <iframe src="https://www.playkeepout.com" marginwidth="0" marginheight="0" frameborder="no"  style="height: 600px; width: 100%; border-width:0px;"> 

 </iframe>

</center>

 </form>

Update, for version 9.0 Enterprise:

<?xml version="1.0"?> 
 <form string="Embedded Webpage" version="7.0" edit="false" create="false"> 
 <div style="position:absolute; left:0; top:0; width:100%; height:100%;"> 
 <iframe src="http://www.playkeepout.com/" width="100%" height="100%" marginwidth="0" marginheight="0" frameborder="no" scrolling="no" style="border-width:0px;"> 
 </iframe> 
 </div> 
 </form>

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Just add an iframe to the view you want the webpage to appear in:

<?xml version="1.0"?>
    <form string="Embedded Webpage" version="7.0"  edit="false">
        <iframe marginheight="0" marginwidth="0" frameborder = "0" 
                src="http://www.openerp.com" width="100%" height="1000"/>
    </form>

UPDATE:

I don't have the problem you have in Chrome:

Using the exact code above, every link inside the IFRAME updates only the IFRAME.

First, the IFRAME was directed to www.openerp.com

Next, I clicked APPS.

Next, I clicked CRM.

Each time the window did not refresh, just the iframe.