Secret SEO Ninja Becky came back from the SEOMoz Pro Training Seminar in Seattle yesterday, and dutifully shared the spoils of her travels with the rest of the Ninjas at home. Probably the coolest thing she brought home is the LDA tool, which was unleashed onto the public on Tuesday by Ben Hendrickson (@bhendrickson).

If you don’t know who Ben Hendrickson is yet, you will now. He’s the genius who essentially reverse engineered the search engine ranking algorithm as it applies to content relevancy. Now in English: He created the LDA tool to show us how relevant our content is to our chosen keyword. This is huge news in SEO, especially since LDA can pretty effectively predict the rank of a site for a specific keyword based solely on the content. Just let that soak in for a second.

Briefly, how to use it: open it up in your favorite browser by going to http://www.seomoz.org/labs/lda (bookmark this one, trust me!). Put your desired keyword into the “Query” box. If you have content you’d like to test, copy and paste that bad boy into the “Document” field. Otherwise, put the URL of the site you’re interested in into the “URL” field, and hit compute relevance. Note that this checks out the whole site, so if you want to look at a specific page only, you should paste the content directly into the “Document” field.

Once it’s done thinking, you’ll get a lovely number like 65%, which is much nicer than yesterday’s random cosine value. This basically means the content on the site or the specific content you put in is 65% relevant to the keyword you chose. You can get a lot more out of that number by comparing it to your largest competitor to see how their content stacks up. Drawing conclusions from there is pretty easy.

The LDA has hundreds, probably thousands of applications for anyone who is interested in how the web works, but I picked just 10 to share with you today to get those gears going.

Probably the most obvious use of this tool is to test your site’s relevance against your competitor’s site for a specific keyword. Follow the instructions above for each site, making note of the number. Generally you can expect the site with higher relevance to rank better.

If your site has better relevance but your competitor is still performing better, consider looking at other known ranking factors, such as back links, site speed, or multimedia.

9. A/B Testing

Yes, I know, we’re not supposed to get lost in A/B testing, so do not go overboard, but hear me out. If you’re copywriting for a site and feel ambitious enough to come up with two copies, pop them into the “Document” field and test their relevancy against the keyword you’re trying to hit.

Version 1:

Version 2:

The tool strips the excerpts down to a set of vocabulary lists. If I had written both excerpts and was wondering which was more likely to rank higher, I’m clearly going to choose Version 2.

Don’t do this for every single page, but a few will give you a good idea if you’re on track or not. It’s a quick and dirty way to get an idea of where your site might rank with the content you’re writing.

8. Vocabulary Lists

If you’re not ambitious enough to write two copies of a page (and really, I can’t blame you there) for A/B testing, you can use the LDA to help you build a vocabulary list. Put your favorite competitor’s site into the LDA for a keyword you like and see what it comes up with. Use that list of words to help guide you as you write the copy for your site.

Using  eyes.com:

7. Relevant Keyword Lists

You can also use that list to help you find other relevant keywords and get a feel for what words are considered related to your query. Use a competitor’s site to help you find the words search engines will group together as synonymous or related.

6. Compare Keyword Lists

This one builds on number 7. You can compare the keywords your competitor’s site is targeting and likely ranking for with the ones that you’re targeting. Do you have any that he doesn’t? Does that scoundrel have a market cornered that you should be a part of? Use this to help you figure out how you can improve your site.

5. Find Content Holes

Test your site’s relevancy against the different keywords that you want to rank for. Is your site relevant for “plastic surgery,” “breast implants,” and “liposuction,” but not “mommy makeovers?” Looks like you should add some content about mommy makeovers!

Since 34% leaves a lot of room for improvement, a personal injury lawyer may find it worthwhile to add some dog bite content!

4. Content Ideas

If you’re just generally looking for ideas on what to write about, you can use the LDA to help you with that, too! You can use your site or a competitor’s to get that giant word list. Skim through and see what inspires you!

3. Find Where to Link to Your New Content

You’ve done the content research, A/B tested it and now are ready to add it to your site. You can quickly see which pages you should link to it from by looking through the word list. Or, better yet, you can compare how relevant two individual keywords are by putting the second keyword into the “Document” field.

If you’re a bariatric surgeon who wants to add a page on heart burn surgery, you can see that your pages on weight loss surgery are relevant, but those on lap band surgery are not. Use the LDA as your guide to making sure your site seems tied together properly.

Option 1: Your page about weight loss surgery

Option 2: Your page about LAP-BAND surgery

The relatedness of heart burn surgery to weight loss surgery is much higher than to LAP-BAND, even though it’s a type of weight loss surgery itself! The weight loss surgery page is the clear winner.

2. Localization Relevance

How well are you targeting your pet localization? Put it into the “Query” field and compare your relevance to that of your favorite competitor’s. If they’re doing better than you are, investigate their site and see how you can target your favorite place better.

1. Compare your keywords head to head

Using the same method as number 3, above, you can see how relevant your keywords are to your keywords. Making sure your keywords are related keeps your site focused and relevant, which the search engines love.

For now, the LDA is graciously offered for free through SEOMoz labs, but I don’t expect that to last for very long. We have a pro account here, and it is absolutely worth it. The SEO tools available through SEOMoz are incredibly helpful and allow us to do better work for our clients.

What other uses for the LDA have you come up with?

9/6/10 edit: For more detailed information about LDA and the LDA Tool, please read Rand Fishkin’s excellent post, Latent Dirichlet Allocation (LDA) and Google’s Rankings are Remarkably Well Correlated.