У вашего броузера проблема в совместимости с HTML5
PLS READ THIS:
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FYI, as of patch 7.11, the new Item Set Creator for the client is out! It's found in on the homescreen--collections--items.
However, this videos' method still works if you're crazy like me and like to do a lot more work than is necessary (or you've made a lot of these and just don't wanna make em all over again)!
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https://www.youtube.com/watch?v=yT0hW9QHhL4
LoL Item Set Editor:
http://lol.item-set.com/#!/editor
Winrar:
http://filehippo.com/download_winrar/64/69823/
This tutorial is for people who've got the new client and want to customize their in-game Items cause the new one wont let you and the legacy client has been RETIRED. Try out this new method. It's easy, it works and it's way better than waiting for Riot to patch Item Sets back in. ENJOY and tell you're friends!
Whoever made this is a scholar and a genius!
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UPDATE: I couldn't get LoL to install onto my crappy Mac (and a virtual machine didnt help either... but the official file path for a Mac is:
Applications/League of Legends (Right click, Show Package Contents)/contents/LoL/Config
let me know how it goes?
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