Hi, Generally, when a market is crossed, it just means that there is significant momentum(buyers/sellers) in it and it has a high probability of moving either way really fast. However, market crosses by itself means nothing. The key is to use the charts to find out if the stock is in play. For example, is the stock breaking key levels; are there bids/offers; is volume shooting up; -- are some of the things to look at. I see in your link that it shows QQQQ as "market crossed". For QQQQ, most likely market crossed means nothing and it is always crossing because of the large influx of buyers and sellers on both sides and it really means nothing.
All electronic markets "cross" every so often, just part and parcel of the system. We teach our traders to bid higher than offers, offer lower than bids anyway for quicker executions, sometimes a second or two will go by with crossed markets. Don