Naming “class” and “id” HTML attributes - dashes vs. underlines [closed]

Answer 1

I would suggest underscore mainly for the reason of a javascript side-effect I'm encountering.

If you were to type the code below into your location bar, you would get an error: 'example-value' is undefined. If the div were named with underscores, it would work.

javascript:alert(example-value.currentStyle.hasLayout);

Answer 2

Actually some external frameworks (javascript, php) have difficulties (bugs?) with using the hypen in id names. I use underscore (so does 960grid) and all works great.