Recently, the http version of Stack Overflow doesn't show voting icons. This is due to a XML error in the svg file that's being served.
- Go to Dictionaries and files in python for example (just picked the top one in my list on the frontpage)
- In Firebug or Chrome dev, highlight the missing vote arrow and locate the cdn url for the background image (in my case http://cdn.sstatic.net/stackoverflow/img/sprites.svg?v=1bc6a0c03b68)
Open that url in a new tab, it will produce
XML Parsing Error: syntax error Location: http://cdn.sstatic.net/stackoverflow/img/sprites.svg?v=1bc6a0c03b68 Line Number 1, Column1: 3-1.7c2,0,3.4,0.8,4.3,1.7c1.2,1.3,1.6,2.9,1.6,5.3C169.7,40.5,169.4,42,168.2,43.3z M165.5,34.6
If you change the url to https://, it will work as it should.
Solution would probably be to redirect http to https for stackoverflow.com.