Is there a reason you are using rho?  If you want it to work like the IE browser on the MK3000, you might have better luck using Enterprise Browser and selecting to deploy using IE instead of webit.  This should be equilvalent to running PocketBrowser.  It won't be exactly the same browser as the MK3000, but it would be more similar than the webkit browser in Rho or Enterprise Browser using Webkit.

Also, if you are running any of our custom browsers (rho, PocketBrowser, Enterprise Browser) there are javascript APIs for the scanner that would allow the developer to capture the barcode scanned without needing a field to have focus (I assume that's why they are trying to do this).

I'm not sure just what you mean by "autofocus". It's a new HTML5 feature:

http://davidwalsh.name/autofocus

I don't think that's what you mean, though.

What is it you are trying to accomplish, and how does it not work as expected?

You have two bits of code above, and not sure which one isn't doing as you expect.

1. You have some code (inline Javascript) that focuses a different field when tbArticleNumber is blurred.

2. You have some code that I guess tries to focus tbArticleNumber initially.

Which of these doesn't work?

You need to wait for document ready before (2). You didn't say if you are using jQuery, so can't tell you how to wait for document ready.

For (1) some browsers may require a timeout. I suggest not using inline Javascript.

If you are using jQuery:

$(document).on('blur', '.tbArticleNumber', function() {
setTimeout(function() {
  $('.tbArticleNumber').focus();
},0);

(Unclear what you are trying to do here, though. You are changing focus back to the same field?)

Note that the timeout value is 0. This should work for most/all browsers. This insures that the .focus() isn't attempted until after the blur event processing is completed.

Actually, you can probably just use autofocus attribute:

http://caniuse.com/#search=autofocus