so at work, I use mac os X snow leopard (10.6). I use Lion (10.7) and Mavericks(10.9) at home. I notice that firefox runs much better on mavericks. Paritcularly the javascript debugger and d3 visualization engine. Today I had to switch to chrome as firefox wasn't stopping at the breakpoints I was setting (snow leopard). I had never had this problem before. Any clue on why this discrepancy between the same code on different os versions? another example: this d3 visualiztion works on mavericks, but fails on both snow leopard and lion. http://bl.ocks.org/mbostock/1062544 thanks