Hello and welcome to the discussion. You can not just copy and paste this code to a html widget, you must 'insert' it using a software like MassReplaceIt for example.
Just create a text box in your Iweb page and place it where you want your widget to appear.
Publish your site to a folder
Open MassReplaceIt software and on the first tab just enter the text you put in Iweb in the first box, for example: 'GoogleTranslateWidget' and in the second box paste the code you provided in your message.
Apply to all your site (You can copy the text box on all your pages if you desire).
Upload your file to your hosting company and look at the result.
Work great for me, look at my page http://www.wesdotphotography.com/Home.html and try it (the only drawback is that your site might look funky when translated).
Good luck
Thierry
+PS: I may receive compensation via google ads if you visit my site.+