The 4xx Errors report contains a bar graph that allows you to view the top 10 requests that resulted in a response code in the 400 range. Typically, a 4xx response code occurs when a request is denied as a result of a client error.
For each asset in the bar graph, you can get a quick sense of how many requests resulted in a 4xx response code by comparing the color-coded portions of the bar corresponding to it. The yellow portion of the bar indicates all of the requests that returned a 4xx response code for that asset. The remaining red portion represents the requests that returned a different response code for that asset.
The data that was used to generate the graph is displayed directly below it.