There are two basic ways how you may bind HTML5 client into your actual page.

A: by using URI as in the attached example iframe_bad_uri.html
src="/software/html5.html?user=mylogin&pass=mypass"

but this approach may have following disadvantages
  1. AdBlockers may refuse such links
  2. Internet filters may filter out such link requests as potential injury.
  3. Mobile browsers may have browser specific char limits for URI requests.

 
B: or by using window.name object as in the attached example iframe_good_name.html
src="/software/html5.html" name="base64_encoded_string" 

This approach has only one disadvantage, it requires enabled JavaScript engine but since HTML5 client is unable to run without JavaScript this limitation is unconsidered.

PS: the attached examples may need extra modifications for your needs so treat it accordingly as code of practice.
To download *.html examples click on it with RIGTH mouse and then choose from context menu "Save as.."