Google released several updates to Webmaster Tools which aim to provide site owners and managers with "more detail and more control" over how a site appears in search results.
Google has added a "change" column next to the impresions, clicks, clickthrough rate (CTR) and position columns. This column is connected to the date range that is specified which will be useful when tring to pinpoint a particular change occurred. (see image below)
And, it gets even better. Now, each query (keyword or phrase) listed links to a query details page which includes a graph of impressions and clicks for that specific query, providing a quick visual of its performance in the search results over time. (see image below)
Below that you will see a table listing of the pages returned in search results along with impressions, clicks and CTR. The data is sortable and can be downloaded as well.
Google has also made some changes to how it handles parameters. Google introduced parameter handling last year which allows webmaster to specify URL parameters and whether they should be ignored or not (essentially you are telling Google it only needs to crawl and index one specific page, not the same page with different parameters). Webmasters now have the ability to choose a specific value among the know values for a given URL parameter (important when the parameter is relevant to the content, but when different values of the parameter lead to similar pages.