Magento Invalid URL on Install
If you are trying to install the Magento shopping cart but can't get past the Configuration step because of a "Response from server is invalid" error?
The cause of this error is most likely the DNS hasn't resolved yet, but whatever the reason, there is an easy way to get around it.
In the Web Access Options panel, simply tick the "Skip Base URL Validation Before the Next Step" box. Make sure your URL is correct, but if so, ticking this box will get you through the Configure step.