You're right, that is odd. For what it's worth, you page works fine in IE10.
I've not been able to find a proper solution for you in the time I have available, but in the meanwhile, have you considered applying a width
or a max-width
to the body text element?
[EDIT]
I can confirm that adding width:100%
to the content-lead
element will work around the problem.
Still not an answer to why the problem is occurring, but at least it's a work-around.
[EDIT again]
Actually, it turns out the above work-around isn't quite as good as I originally thought. The width:100%
only worked for me because I was playing in the console. Doing it in CSS has no effect.
Setting a fixed width may help, or possibly using CSS calc()
if a completely fixed width isn't suitable.