Yes it is but they will have adjusted their spread to account for how they believe the market will open. This was discussed earlier today on these boards because the Spreadbetting companies had adjusted their spread on the Dow Jones downwards by about 170 points before the open.
To be honest Awllee, your guess will be as good as anyone else as to what a market will do on the open of the next day. It is not something I would do but it may well suit you. Whatever you do I wish you all the best.