The market was up yesterday, why is my fund down?

Funds are usually priced at midday, so any changes in the market are unlikely to be reflected in its performance, and therefore your account, by the time markets close. 

Also, unless you have a tracker fund which follows the index performance directly, the investments in your fund will behave differently to the market. This means there won't be a direct relationship between rises in the market and your fund's value.