This is a single-class classification problems. Your predictions should be a number in the range [0,1] where 0 indicates 0% probability of comment being an insult, and 1 represents 100% insult.
All predictions should be in the first column of your submission file. Please see 'sample_submissions_null.csv" for the correct format.
The evaluation metric for this competition is the Area under the Receiver Operating Curve (AUC). This evaluation metric penalizes wrong predictions made with high probability. For more about this metric, check out the AUC page on the Kaggle Wiki.