Here is a screenshot of what the above linked page looks like on IE 11 on Windows 7.
[What the post says is a silly mistake, by the way

. But it's a lesson in humility for me to stick with what I originally linked, since this thread is about formatting, not content]
The 'cos' is supposed to be non-italic, because I prefaced it with a backslash in the Latex code. But the x would normally be italic, and isn't.
Also, the subscripts on summations are mis-aligned, as in this pic:
The latex code used for that was
||Ax||_{\infty} = max_i \left\vert \sum_{j} a_{ij} x_j\right\vert\leq max_i \sum_{j} |a_{ij} x_j|
I noticed that when I open a page that has latex on it, the following happens:
- First it shows the latex code
- Next it shows a rendering in all italic
- Last it Shows a rendering in all non-italic.
I don't know if that helps.
I forgot to check at home last night on Firefox+Linux. I'll make a note to check tonight.
EDIT: I'm at home now and have checked it on Firefox+Linux and it looks fine.