Why do I get this message when I tried Activitystarter

MIT App Inventor Help
2

According to

  • Opening a browser to a specified web page. Assuming the page you want to go to is “www.facebook.com” (feel free to substitute your own choice), set the properties to:
    • Action : android.intent.action.VIEW
    • DataUri : http://www.facebook.com

your fuzzy blocks image looks okay.

Maybe if you download the blocks directly we could see something.

Please download and post each of those event block(s)/procedures here ...
(sample video)