HARD FORK BLOCK 626,000
On block 626,000 the difficulty algorithm will change for both PoW and PoS. PoS will use Qtum's difficulty adjust. PoW will use the same solution used by Dash. The current difficulty algorithm tends to oscillate either too high or too low. Having the difficulty adjusted separately for each type of block generally allows one type to cover for the other when the difficulty is left too high, but a more accurate difficulty solution is required hence the hard fork.
No longer provide contract transactions to getblocktemplate. This is typically used by pools or mining software that construct the entire block external to HTMLCOIN. As no external mining software that creates blocks has yet added support for contract refund transactions in the coinbase, then providing contract transactions can prove problematic, as refund transactions not being present will cause those blocks to be rejected by the network. This combined with the oscillating difficulty adjust could leave HTMLCOIN with long periods of no blocks, this has been temporarily remedied by contacting the major mining pools and asking them to disable contract staking. This change is not part of the consensus rules so external mining software can enable contract transactions in getblocktemplate, if they succeed in supporting contract refund transactions.
Combine loops in the soon to be legacy difficulty adjust algorithm to prevent looping over the same set of blocks twice.