Wm Morrison Supermarkets shareholders are down 11% over twelve months (even including dividends), which isn't far from the market return of -12%. Longer term investors wouldn't be so upset, since they would have made 4%, each year, over five years. If the stock price has been impacted by changing sentiment, rather than deteriorating business conditions, it could spell opportunity. While it is well worth considering the different impacts that market conditions can have on the share price, there are other factors that are even more important. Take risks, for example - Wm Morrison Supermarkets has 1 warning sign we think you should be aware of.