I run in the following cross-browser issue while investigating the previous issue [1].
The specification defined the value passed to these methods as a string with the following property:
# The key must resolve to a number between 0 and 1, or the rule is ignored.
And indeed, if you do findRule("1") or deleteRule("0.5"), IE dutifully finds/removes the 100% and 50% keyframes, respectively.
No other browser does this, however. Gecko, WebKit and Blink all expect "100%" and "50%"
To mitigate any compat issues, one possible compromise would be to require browsers to support both in the future.
[1] Received on Friday, 21 March 2014 01:21:45 UTC