The makeId utility generates a random DOM identifier, which is a mixture of alphanumeric characters. Sometimes this results in an identifier that starts with a number, which is not valid in HTML4 (but is in HTML5). This caused a problem in Cloud when integrating with Recurly, since the latter's code would choke on IDs that started with numbers. We were able to work around this by setting explicit IDs, however it would be nice to avoid this issue more widely by preventing it in makeId.

See: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/id