keyword density?

I'd not pay too much attention to any automated tool.

Simply put every single word that is not a search query you intend to use to pull in visitors dillutes your keyword frequency.

But don't stress too much about keyword frequency and such with forums. Heck you don't even control all the content do you?

The answer about impact is probably that it will make absolutely no difference for your site.

Where that makes a difference is at the forefront of SEO, when you are going head to head with other SEOs and you have total control over every single element of the site.

For example, your page names make more difference. The text IN the URL is the most important, after the text in the domain. With the text in the title next.

With phpbb you don't even control the URL text. So you are already using huge disadvantages.

Things like keyword density only help give a slight (ever so slight) push over the edge.

I run administer some very competitive commercial sites in which each space, dot and letter is analyzed. In that setting it is important. But don't worry about it in your forum and certainly don't pay too much attention to any automated SEO tool.

As a side note, the only thing I've ever used a tool like that for is to check to see if I've put the keywords in too many times. Too much is considered "keyword spamming" by search engines.

what's too many times per keyword or keywords total?

That depends. It differs for each search engine and is only one factor in algorithims that constantly change.

It has more to do with density than frequency though.

As long as a human wouldn't think it sounds absurd it's usually ok. Don't repeat for the sake of it. Repeat only a few times to create different queries that will bring up the page.

It's better to repeat synonyms.

For example forums, message boards, bbs etc are all different. Using them all would be better than repeating "forums".

Ultimately you need to realize that the algorithim of a good search engine will always try to determine real relevance, not fake relevance.

So it's really a balance. You need to optimize but not deceive. This isn't just a principle of SEO but the site as a whole.

Remember the idea is to make it optimized for the humans who will use it first, not the robots that index it.

and do you think that the robots do a good job of this or are they too picky?

For instance, I wanted to start getting reciprocal links but I remember somewhere that you warned against link pages or something like that. A user wouldn't mind the page so long as it was categorized and organized appropriately so they could find the information they wanted quickly and easily, but I don't know how a robot would look at it or how they treat it at all since not all the links are directly relevant in content to the site or how I would determine the difference between what the robot thinks is relevant versus the human.

Actually the robot just fetches, the algo is what we are really talking about.

But to answer your question:

Link pages are not bad. It's a link "farm" that is.

For example, dmoz links to millions of pages. But they ahve a higher pagerank than most webmasters can dream of.

What search engines are penalizing for is an attempt to boost page rank artificially through link farms.

How they determine what's simply relevant reciprocal linking and what's a link farm is based on very complex algos.

For example, some of it is human input. If you use software or a service for "link exchange" then you might be using something they automatically penalize for.

Other than things like that just try to keep less than 50 links on a page and you should be fine.

Do note that who links to you rarely ever hurts you, who you link to does.

So if you link to a site that has been flagged for link farming then you might be penalized.

So in short, make it useful (less than 50 links per page) and don't link to sites that you suspect are not of good quality.

And don't use certain tactics like hidden links.

how did you ever learn all of this???

I work with search engine optimization both as a hobby and commercially.