This error indicates that an old version of index-mobile.html is used. In the new template, the body contains a '<div id="content"></div>'. Make sure to add the new index-mobile.html to your theme and redeploy first, before testing it. (Otherwise the gzip file might get in the way)
It is recommended to grab a fresh index-mobile.html, and re-apply your customizations. Note: to get a clean index-mobile.html deploy the project without a theme.
Maybe the index-mobile.html is not updated. Create a new 4.0 project and copy the index-mobilte.html?
Or maybe clear the browser cache.
I have cleared the browser cache and created a new 4.0 project and copied all index html files including the .gzip files, but still same error.
Removed all index-mobile html and gz files. Then I put index-mobile html files from a new project in theme files and redeployed and cleared cache. Thanks for all the quick help.