How you can lose money by solely relying on moneycontrol.com or brokerage sites for your financial analysis/data.

For a retail investor, these sites seem a godsend. Multiple years data, covering income statement, balance sheet, cash flow and other information(notes to accounts etc), often downloadable in Excel. And depending on the site, one can read the latest annual report online, see graphically displayed ratios or do peer analysis. Little wonder then, that one may see little utility in the laborious process of downloading the annual report from company/NSE website and then poring through it. Ordinarily, I would agree with you on that, but after some near-mishaps from using that data,  I realized that if not careful, one could base the decisions on wrong information and lose a chunk of money. Below are some pointers to keep in mind while using these sites. In all fairness, I must admit that websites like moneycontrol.com/Edelweiss have a good interface and address most of this. But it is for the investor to be aware and confident.

1. Standalone or consolidated data? Some websites may update standalone data by default, even if the company releases consolidated data. While this would generally conservative(as subsidiaries should be profitable), this may understate the real profit for companies in lossmaking growth areas etc. Hence, be aware of the data especially for book value and profits. It also affects infra companies like RInfra whose profits are centred in the operating subsidiaries.
2. Income from continuing operations/restated data updated:-When companies divest their main arms like how Piramal Healthcare did a year back, the common practice abroad is to release a 5yr proforma data of the remaining continuing operations. While Indian companies do not do so, remember that the dramatic improvements in the ratios you see on the website, maybe simply because the company divested its lossmaking operations/did some corporate restructuring to take it off its books.
3. Whether latest book value updated:-Some websites do not update the book value despite the 1H'12 earnings release containing a brief snapshop of that;albeit unaudited. That makes a material difference for companies like SKS Microfinance, which announce a sizeable loss every quarter!
4. Is the EPS data for FY11/TTM:-For the P/E ratio, do check whether the EPS data is for the previous completed year, or trailing 12 months
5. Definition of ratios:-Before relying on unaudited non GAAP numbers like operating earnings/EBITDA etc, try to match those numbers to the income statement, since each website typically has its own definition.
6. Adjusting shareprice graphs/data for splits/rights issues:-This is a very common source of mistakes, where a share post 10:1 split may trigger a stock screener for losing 80% of its value within 1yr! While a glance at the graph would make it clear to any savvy investor, be alert for such events while analyzing stocks which have lost enormous value in that year. 

 This list is just the tip of the iceberg, and investors should take due care remembering the maxim of 'garbage in garbage out'