popup

My method for this involves using Javascript. Since Google does not allow Javascript to be inserted directly in a page you have to use a gadget. There are two methods shown here.

Note that when your gadget links to a http: URL you will see am "unsafe content" warning in Google (https:) sites. You must click to allow it. Try linking to https URLs to avoid this.
  1. Create your own gadget using the gadget editor.
  2. Use the Embed Gadget and place the code into it.
This is the code for the gadget:
   (Modify the code in red for your site)
 
<?xml version="1.0" encoding="UTF-8"?><Module>
<ModulePrefs title="popup" /><Content type="html"><![CDATA[<a href="javascript:void(0)"onclick="window.open('http://w8shi.net','miniwin',
'left=25,top=25,screenX=25,screenY=25,toolbar=0,location=0,
directories=0,status=1,menubar=0,scrollbars=1,resizable=1,width=700,height=600'); return false;"> W8SHI in a popup window.</a>]]></Content></Module>
 
The gadget URL is: http://hosting.gmodules.com/ig/gadgets/file/117770694006921265528/popup.xml

Information about the window.open method
 
 
 
You can skip creating a Gadget by using the Embed Gadget:
  1. Insert
  2. More gadgets
  3. Select Featured Gadgets
  4. Select Embed Gadget and add it to your page
  5. Insert code as in the box below into the gadget
  6. Modify the code in red for your site
  7. Un-tick Place border around gadget and Include title
 
 
<a href="javascript:void(0)"onclick="window.open('https://www.google.com',
'miniwin','left=25,top=25,screenX=25,
screenY=25,toolbar=0,location=0,
directories=0,status=1,menubar=0,scrollbars=1,resizable=1,
width=700,height=600'); return false;">Google in a popup window.</a>


To use an image instead of a text link:
 <a href="javascript:void(0)"onclick="window.open('https://www.google.com',
'miniwin','left=25,top=25,screenX=25,
screenY=25,toolbar=0,location=0,
directories=0,status=1,menubar=0,scrollbars=1,resizable=1,
width=700,height=600'); return false;"><img src="https://www.google.com/images/logos/ps_logo2.png" title="Google in a popup window"></a>