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You don't need a sitemap on any site, but its a good thing to do on any site if you want the best SEO. The document type doesn't matter because the engine crawlers don't change based on the version of the standard you're using.

If you decide to change things later you can update your canonical tags and/or use a 301 redirect. Based on the information on the Google webmasters blog, it appears they consider the canonical tag on every crawl. You can read more from Google on it here:

http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html

Of course, just because you can change it doesn't mean you should. Switching them around will probably cause a period in which Google is unsure of the actual canonical page, and you may see a drop in rankings while it is sorted out.

This looks more like a dynamic site using AJAX, rather than anchors in the page like you're thinking.

See: http://code.google.com/web/ajaxcrawling/docs/getting-started.html

No funny stuff. The page you see is the page google intended to show you, with all the SEO value for the page itself being responsible for its spot in the SERPs.

Start with making sure your website has great informative content. After you have your basic site populated, you can start to develop a "blog" strategy for adding more content and targeting more keywords. I put blog in quotes because this could take the form of a wordpress install at /blog on your site, or it could be an articles list, or a knowledgebase of answers, etc. Just make sure that you've got a strategy to continually add new content, and target more and longer-tail keywords. Then, if your blog posts can be tied into a current event, or if your organization is a news-maker itself you can re-write those blog posts and distribute them as press releases via prweb.com and others.

If you have enough content and time to manage the SEO on the 2nd domain, I'd say go for it. What you want to avoid is duplicating your content, or cannibalizing your own keywords on the main site.

If you don't have any new keywords you want to pursue, don't have the time to properly SEO the domain, or don't have enough content for a second site, I'd say go for the redirect.

EDIT: You should also know that exact match keywords in domains is one of the less important ranking factors, and most agree it will continue to become less important.

Option 2. You'll want to use a 301 redirect to send all traffic going to the old URLs straight to the new URL. Your users may be a little disoriented seeing the new URL but they'll at least arrive to the information they're looking for. The robots will see your new URL and assign the link juice there. Win for robots and humans.

Unless you don't care that much, in which case option 1 is clearly the easiest.

Two ways:

1. Find out where Google followed a link to the non-existent category pages, and get those links removed and the category pages redirected or blocked as EGOL mentioned.

2. Change your code so that non-existent categories show a 404 page, preferably a 404 crafted to gently push your user to something they may be interested in.

Have you already tried www.xml-sitemaps.com ? It will crawl and generate a sitemap in whatever format you want.

However, in terms of reporting problems I've found the SEOmoz crawler and related tools to be invaluable.

You can save your sitemap in xml format from the above site, and use that to submit to search engines.

In general, the latest thinking regarding link building says your goal is to ultimately build a relationship with site owners that lead naturally to links and other collaboration.

You need to use regular expressions in your .htaccess file to create a blanket rule that redirects all pages on your site. Here is an example:

<ifmodule mod_rewrite.c="">RewriteEngine on
  # Redirect non-www to www
  RewriteCond %{HTTP_HOST} !^www.mydomain.com [NC]
  RewriteRule ^(.*)$ http://www.mydomain.com/$1 [R=301,L]
 
  # Redirect index.html to the root
  RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index.html
  RewriteRule ^index.html$ http://www.mydomain.com/ [R=301,L]</ifmodule>

If you're using a separate CMS for your blog (and maybe even if you're not) you will want to make sure the .htaccess file for that is properly set as well. Look for this file in your blog folder and if one exists adapt the code above to include your blog folders URL.

You should put them in folders in order to pass your domain authority to them. If you put them in subdomains you'll have to start building their domain authority from scratch.

Woah, quicker on the draw! I yield to you, sir

• Yelp and Pinterest
• social sharing like Reddit, Delicious, StumbleUpon
• If your brand is notable, Wikipedia
• All the locals: Manta, CitySearch, etc.
• Industry specific sites like review sites
• If you're in some kind of knowledge industry you can do Quora and StackExchange.

Yes absolutely change it over from tables. A lot of the work the search engines are doing lately is to understand and interpret semantic markup. A table based layout is pretty much the antithesis of semantic markup.

It doesn't seem like a presentation issue like tables could effect your SEO, but you're missing out on all the goodness of rich, semantic html.

Here's a good intro: http://www.webdesignfromscratch.com/html-css/semantic-html/

The method currently in vogue, and also SEO friendly, is a javascript based lightbox. Here is one example.

It degrades nicely for users without javascript (like a crawler bot) because its a normal link that is just rendered differently for the java enabled viewer.

Google has been looking at CSS for a while now, but I think its only to stop black hat tricks like z-indexing away filler text or using H1 tags where they're not actually headlines. An overflow:scroll is just a way of visually organizing your content, so I can't see any good reason that Google would penalize this. Of course, I don't have data to back this up so take it for what its worth.

What they could conceivably do is subtract some weight from the text inside the element with the overflow property. If there are two paragraphs on a page, one with overflow, one without, it could argued that the paragraph without the overflow scroll bars can be seen as slightly more important, since its presented in full.

Technically its a lot more involved than a blog, probably requiring more bandwidth and processing power if it becomes successful. And it requires more technical know-how to get it set up properly. Then the challenges of building and maintaining an online community are significantly greater than just publishing a blog and attracting a readership.

But again, if you can pull it off you'll have a fantastic resource and a great way to market your brand.

According to teh Google you'll want to create a second sitemap specifically for your mobile pages. See: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=34648

Every section of your robots.txt file consists of declaring the agents the rules will apply to, and then the rules themselves.

In your file the User-Agent: * is the first part, where you are saying the following rules apply to every type of visitor. But if you only have that, and no actual rules, then you don't really need a robots.txt file. The "normal" file Jordan refers to in his answer is probably a good best practice, but isn't technically necessary.

Check your external links. Are they mostly pointing to the category page instead of your home page? For the keywords you're trying to rank for, do they appear in anchor tag text pointing to the category page instead of your home page? I ask these questions to try to figure out why it appears your category page has gotten more page authority than your home page. Once you find the answer to that, the way to fix it should present itself.