All from css-tricks:
There are times when a really long string of text can overflow the container of a layout.
URL’s don’t typically have spaces in them, so they are often culprits.
Here’s a big snippet with all the CSS players involved:
/* These are technically the same, but use both */
/* This is the dangerous one in WebKit, as it breaks things wherever */
/* Instead use this non-standard one: */
/* Adds a hyphen where the word breaks, if supported (No Blink) */