The police in the UK actually have a map of all crimes that have taken place recently in a neighbourhood [1], I think this is a better way of going about the issue, crime rates seem to correlate more closely to safety than how a place looks, I think.
I had this problem too, Turns out I have the HTTPS Everywhere plugin for chrome so the page loaded over HTTPS, so mathjax wasn't allowed to load as it was loading from a plain HTTP server
Personally, I find that eBay (at least in the UK) has proven itself to have the best shipping, selection, service and price. Especially with it's new "Fast and free" promotion
[1] http://www.police.uk/