Chalk this tip up to something you probably didn't know you could do. You can inspect a web site running on iOS using desktop Safari's Web Inspector.
Here's how you can set up your iOS device to inspect pages remotely:
Enable Web Inspector for Mobile Safari in Settings
On the iOS device, go to the Settings.app and go to the settings for Safari.
Click on Advanced and make sure the toggle for Web Inspector is turned on.
Enable the Develop Menu in Safari
In Safari, open up Preferences...
Next click on the Advanced tab.
Make sure the Show Develop menu in menu bar is checked
Connect your iOS device to your Macintosh
Connect your iOS device to your computer with your charging/data transfer cable and connect it to the USB port on your computer.
Navigate to a Page in Mobile Safari and Open up Web Inspector
You'll need to have Mobile Safari open on your iOS device before you can open the web inspector.
Once you're ready open up Safari on your Macintosh and click on the Develop menu. You'll see a list of devices including the iOS device that's connected. If you choose that device you'll then get a list of web pages that are open and once you choose a page the web inspector will open.
Now you'll be able to inspect and directly manipulate elements on the page just like you would if you were inspecting right in Safari.