IE6 compatibility fix
IE6 compatibility fix

CloCkWeRX/tipsy,modulexcite/tipsy,CliftonH/tipsy,atlassian/tipsy,etlgfx/tipsy,CloCkWeRX/tipsy,bigmlcom/tipsy,jlsherrill/tipsy,DataDog/tipsy,wlaurance/tipsy-browserify,rakesh-sankar/tipsy,rakesh-sankar/tipsy,samuelcole/tipsy,1999/tipsy,jaz303/tipsy,jaz303/tipsy,MartinMartimeo/tipsy,DataDog/tipsy,CliftonH/tipsy,atlassian/tipsy,jlsherrill/tipsy,modulexcite/tipsy,bigmlcom/tipsy,etlgfx/tipsy,justintung/tipsy,justintung/tipsy