This version of the site works on Bitcoin/Litecoin TESTNET. It means that bitcoins/litecoins aren't real and you can safely experiment without fear of losing any money. Be sure you install a Bitcoin/Litecoin TESTNET wallet though: read up our manual on how to do that in the FAQ/Help.
Please, be aware that all trades happening on testnet.hodlhodl.com are with TESTNET bitcoins/litecoins. Never send any actual funds for bitcoins/litecoins received on testnet.hodlhodl.com.