By default the iPad will capitalize the first letter in a sentence. But with my application the login page requires an email address and these are typically in al lower case.
Safari forces the first letter of the email address into upper case, e.g. Jones@example.com - but this does not match the text in the application's databases (firstname.lastname@example.org).
My app doesn't force text into lower case on its end (and it shouldn't !), which means that I could not login to my site. And in this case using the SHIFT key on the keyboard does not let you enter the first letter in lower case.
The solution is for the User of the iPad to go to Settings -> General -> Keyboard and set Auto-Capitalization to Off.
This is a really bad default setting - yes, it can be useful if you are entering regular text - but it's not that useful...
I can't expect my users to deal with this on their end. I could force all email address into lower case in my application and that is probably what I'll end up doing.
HTML5 forms can define that a text entry box represents an email address. This adds convenience when entering from a mobile device (the keyboard can display a '.com' key, for example). Whether or not using this has any effect on auto-capitalization I have yet to test.