Google made a couple AdWords-related announcements advertisers will want to take note of.

For one, they will soon offer ad group level impression share metrics for the search and display networks.

Advertisers will be able to use this data to better identify high performing ad groups that aren’t capturing the majority of available impressions, Google says.

Within the next few weeks, advertisers will start seeing three new columns that can be added to the ad groups tab. These are: Impr. Share, Lost IS (Rank) and Exact Match IS. Impr. Share shows the percentage of impressions you received divided by the estimated number of impressions you were eligible to receive. Lost IS (Rank) shows the share of impressions lost due to your d Rank. Exact Match IS (for the search network only) shows the percentage of impressions you received for searches that exactly matched your keyword divided by the estimated number of exact match impressions you were eligible to receive.

Additionally, Google is also planning an algorithm update to provide more accurate campaign impression share metrics. Changes will include: refined campaign-level stats and once-a-day updates.

“Since we are improving our algorithms, we will update all campaign-level impression share metrics back to May 2011,” says Katie Miller of Google’s Inside AdWords crew. “As a result, you will no longer be able to see campaign-level historical impression share metrics before May 2011.”

“In order to calculate your impression share metrics with a greater degree of accuracy, we will update all impression share metrics once per day (approximately noon Pacific Time [GTM-8]),” she says. “As a result, the impression share data that you see will not reflect impression share for the current day, and may not include the previous day’s impression share as well (depending on what time of the day you run your report).”

These changes will start rolling out globally on January 30.

In a separate announcement, Google announced that it has rolled out two improvements to Automated Rules in AdWords: an increase to the rule limit to 100 (from 10) and the ability to undo changes made by a rule.

“In the event that a rule doesn’t make the changes that you expect, you can easily undo them by clicking the ‘Undo’ button in the Logs table,” says product marketing manager Andrew Truong. “We hope that undo can help you feel more comfortable experimenting with Automated Rules. You can try out new strategies for a few days and quickly return to the state in which you started if you’re not happy with the performance.”