Welcome to the Q&A Forum

Dr. Pete has a good post about this at http://www.seomoz.org/blog/how-many-links-is-too-many

What CMS are you using?  If it is wordpress, there is a plugin that allows you to configure when google is asked to crawl your site and you can set it up so that they only crawl your "archives" monthly and set up how often you have new content on the site.  it is called WP Robots Txt

Hi, Have your pages been crawled and indexed since you changed them?  We will need more information to learn more about the problem.

Hey Giles... Tracking down and correcting these 404 links is going to take a wee bit of work in Excel, since the SeoMoz report doesn't show everything you need in the simplified page view. You're going to have to download the error report as a CSV sort it to make the 404 error pages easy to find use the extra info in the downloaded report to show you where the link is that needs to be fixed When you're on the 4xx (Client Error) page, you'll notice that there's a dropdown in the top right corner that will allow you to export as CSV. When you do this, you'll get a csv file (spreadsheet) that you can open in Excel. When you open it, you'll find that it contains ALL the errors that SEOMoz found, not just the 404s, plus a bunch of extra, useful info. So first step is to sort the whole table by Column D - the 4xx (Client Error) column. If you sort by smallest to largest, your table will now show the 404 error pages (TRUE) at the top of the table.. The first column (URL) is the page that is missing, causing the 404 error. (The same URLs that show in the screenshot you provided). Here's the kicker: the LAST column in the whole sheet (titled Referrer) shows the page that contains the link pointing to the missing page. This is the info you need that isn't included in the simplified page report you get on the SEOMoz website Now that you know the URL that contains the broken link, it's a simple matter of going to that page, finding the link and either deleting it or pointing it to a new, working page. (Easiest way is to "view source" of the page and use CTRL F to find the broken page's URL. It may be hidden in an href that you wouldn't find by just searching the visible text on the page.) Does that get you what you need? Paul