You will have a Short Margin situation, if ratio of the balance taking into account profit/loss of the open positions to the margin value, reaches 10%.
When facing a Short Margin, that is when margin level equals to 10%, positions will be closed, starting from the most unprofitable ones.
IFC Markets offers a free demo account for NetTradeX, MetaTrader 4 and MetaTrader 5 trading platforms where you can see the real numbers without risking your own funds. Demo accounts do not expire.
For beginners, IFC Markets provides educational materials for the beginners.
Educational part of their website covers all the basics of trading in Forex and CFD markets, technical analysis and much more.
Also they have several educational books that will be useful for the newcomers. For more information, please, go to trading books section.