As discussed in previous posts, if you are using Google AdWords, or plan to use it, you need to be aware of some of the default settings and features that will cause you to pay more for each click, and how to avoid those hidden charges.

The number of keywords or keyword phrases in each of your ad groups is yet another small feature that can have a BIG impact on your bottom line. (If you’d like to see how much of an impact, check out the Google Adwords Tax Calculator.)
Let’s say you have 1,000 keywords defining your products or services. You’ve put them all into one ad group and now you need to create ad copy. You should create multiple ad copy for testing and targeting. Your ad copy should reflect your keywords, but since you have 1,000 keywords stuffed in one ad group, it is impossible for your ad copy to be targeted to a specific product or service. If your ad copy doesn’t target your keywords, which should reflect the content on your landing page, your click-through-rate will decrease, which will cause your cost-per-click (or CPC) to increase.
Sadly, nothing is simple. Let me explain further.
The reason that stuffing all 1,000 keywords into one ad group will decrease your click-through-rate, is because if someone Googles your keyword, and your ad copy appears, the relevant keyword (if it’s in your ad copy!) will be bolded, which guides people to click on your ad. Testing has proved that if ad copy is relevant to what the searcher is searching for, the searcher will be more likely to click on your ad.
Not writing relevant ad copy decreases your click-through-rate, which will signal to Google Adwords that your ad is not relevant, causing your cost-per-click to INCREASE. Totally not cool.
To avoid this debacle, it is generally good practice to limit the number of keywords per ad group. There is much debate over the “right” ratio of keywords to ad group, but a good rule of thumb is to only cover the keywords of the landing page to which you are directing traffic. Which brings us to another point: Deep Linking! Don’t send searchers to your home page (unless they are seeking your brand, specifically) — send them to a specific product/service page.
For example: You are a baker and you offer five products (pastries, pies, bread, cakes, and muffins). One of your keywords is “blueberry pie”. When someone searches for “blueberry pie”, you do not want them to see ad copy that reads:
Get a bunch of baked goods here
The best bakery in Pittsburgh
www.generic-bakery.com
Instead, your ad copy should reflect the content on the page that you are sending your paid visitors to. For example:
Our pies taste just like Grandma’s
Apple, Cherry, & Blueberry Pie -
www.generic-bakery.com/pies
This way, when someone searches “Blueberry Pies” – they will get precisely what they asked for, be more likely to click on your ad, and, if your website is enticing enough, be more likely to EAT YOUR PIE. Win!
All of this was a round-about-way of explaining WHY you don’t want to have all your keywords in one ad group, nor do you want to have keywords pertaining to your pastries in the same ad group as keywords pertaining to your blueberry pie.
You could even break it up further and have a landing page on your website for blueberry pies, apple pies, and cherry pies with three separate ad groups that reflect only the keywords and ad copy for that particular type of pie.
Takeaway: If you can break down each ad group to only hold 10-20 keywords, you’re doing pretty darn good.
I would love to hear your thoughts about the “right” number of keywords for an ad group, or about your experience on “The Hidden Costs of Adwords”!
If you’re really into Adwords, be sure to read my other two posts on The Hidden Costs of AdWords – In the first post I show you why keyword matching is important and in the second post, why you should be using negative keywords.