IOS – How to log in into iCloud.com from an iPhone

This is not possible, nor was it possible with Mobile Me. Particularly irritating when a number of people share an iPad and don't want to enable full email for each other for example. I'm afraid there is no way around it, unless perhaps you can download a different browser from the App Store that will enable you to change your user agent string to trick the website into thinking you are using Firefox or something that isn't mobile safari.

You can do this by signing out of that iCloud account. Open the Settings.app and go to iCloud. Then select "Delete Account". Not to worry, this doesn't delete any information from your device, as long as you choose "Keep on iPhone" after signing out of that iCloud account. It will display a prompt after you select "Delete Account", and give you the option of keeping iCloud contacts, calendars, and such on your phone. Like I just mentioned, you will want to select "Keep on iPhone" when facing this prompt. After signing out of iCloud, create an Apple ID (there should be a way on the iPhone itself), and sign into it.

As a side note, unfortunately, you will likely have to purchase any music, or apps, again, that were purchased on his Apple ID. The apps that were purchased with his Apple ID will continue to function, but you will no longer be able to update them, and consequently, the need will likely arise that you will need to purchase them again.