Although I generally look at the S&P 500 to get a feel for the market's trend, it's a good idea to see what other stock indexes are doing. Two of them are giving warning signals. Chart 1 shows the S&P 400 Mid Cap Index (MID) starting to meet resistance along its 2011 highs. That's a logical spot to expect some profit-taking to develop. Chart 2 shows the NYSE Composite Index which has also yet to clear its 2011 high. I suspect that's because of its heavier weight in commodity-related stocks which have been market laggards. Chart 2 shows the NYSE slipping below its 50-day average which is a sign of weakness (blue circle). Its RSI line (top of chart) and MACD lines (along bottom) have turned down. That's another warning sign.