Using Dan Stoll‌'s excellent walkthrough in Nintex App Studio for the win‌ I started looking at the new custom content functionality in Nintex Mobile App Studio.  It was all going absolute great guns; I had a custom home page with links that would open various apps on my phone (to call, text, read documentation etc) but I had this rather odd issue when I clicked on the sms link that was constructed similar to that below:

<p>
<a href="sms:+1-111-222-3333&body=Love%20your%20work." class="button">SMS JOGA HQ</a>
</p>

My android phone (used for testing only - I am an apple girl through and through) kept giving me this error once I returned to the app from sending a message:

I did a search on here and on Google for "net::ERR_UNKNOWN_URL_SCHEME" and lots of things came back actually which was a little overwhelming trying to work out which advice to listen to, so I went with the simplest first which was in this resource:

http://stackoverflow.com/questions/24697429/getting-neterr-unknown-url-scheme-while-calling-telephone-number-from-html-pag

Basically, add target="_blank" to the link.  It worked  and as yet I haven't found any negative impact.

Thought it would be good to share this in case anyone else gets the same issue!