Given a block container
this is a very long string which contains a bunch of characters that I want to break at container edges.
>
There's a CSS3 property called word-break that may be of some use to you in future.
More information is available here: http://www.css3.com/css-word-break/
The break-all value looks to do the thing you're asking for:
Useful where content contains a majority of Asian character set content, to which this value behaves like ‘normal’. Non-Asian character set content may be arbitrarily broken across lines.
As for more supported versions of CSS, I don't believe there's a way you can do this.