New CMS system - 100,000 old urls - use robots.txt to block?

[Blenny]

Hello.

My website has recently switched to a new CMS system.

Over the last 10 years or so, we've used 3 different CMS systems on our current domain. As expected, this has resulted in lots of urls.

Up until this most recent iteration, we were unable to 301 redirect or use any page-level indexation techniques like rel 'canonical'

Using SEOmoz's tools and GWMT, I've been able to locate and redirect all pertinent, page-rank bearing, "older" urls to their new counterparts..however, according to Google Webmaster tools 'Not Found' report, there are literally over 100,000 additional urls out there it's trying to find.

My question is, is there an advantage to using robots.txt to stop search engines from looking for some of these older directories? Currently, we allow everything - only using page level robots tags to disallow where necessary.

Thanks!

[Mark_Jay_Apsey_Jr.]

Loaded question without knowing exactly what you are doing.....but let me offer this advice. Stop the bleeding with robots.txt. This is the easiest way to quickly resolve that many "not found".

Then you can slowly pick away at the issue and figure out if some of the "not founds" really  have content and it is sending them to the wrong area....

On a recent project we had over 200,000 additional url's "not found". We stopped the bleeding and then slowly over the course of a month, spending a couple hours a week, found another 5,000 pages of content that we redirected correctly and removed the robots....

Good luck.

[Blenny]

Thanks a lot! I should have been a little more specific..but, my exact question would be, if I move the crawlers' attention away from these 'Not Found' pages, will that benefit the indexation of the now valid pages? Are the 'Not Found's' really a concern? Will this help my indexation and/or ranking?

Thanks!

[Mark_Jay_Apsey_Jr.]

Absolutely. Not founds and no content are a concern. This will help your ranking....

[Dr-Pete]

I've honestly had mixed luck with using Robots.txt to block pages that have already been indexed. It tends to be unreliable at a large scale (good for prevention, poor for cures). I endorsed @Optimize, though, because if Robots.txt is your only option, it can help "stop the bleeding". Sometimes, you use the best you have.

It's a bit trickier with 404s ("Not Found"). Technically, there's nothing wrong with having 404s (and it's a very valid signal for SEO), but if you create 100,000 all at once, that can sometimes give raise red flags with Google. Some kind of mass-removal may prevent problems from Google crawling thousands of not founds all at once.

If these pages are isolated in a folder, then you can use Google Webmaster Tools to remove the entire folder (after you block it). This is MUCH faster than Robots.txt alone, but you need to make sure everything in the folder can be dumped out of the index.

[Blenny]

Thanks for the advice! The previous website did have a robots.txt file with a few wild cards declared. A lot of the urls I'm seeing are NOT indexed anymore and haven't been for many years.

So, I think the 'stop the bleeding' method will work, and I'll just have to proceed with investigating and applying 301s as necessary.

Any idea what kind of an impact this is having on our rankings? I submitted a valid sitemap, crawl paths are good, and major 301s are in place. We've been hit particularly hard in Bing.

Thanks!

[Dr-Pete]

It can be really tough to gauge the impact - it depends on how suddenly the 404s popped up, how many you're seeing (webmaster tools, for Google and Bing, is probably the best place to check) and how that number compares to your overall index. In most cases, it's a temporary problem and the engines will sort it out and de-index the 404'ed pages.

I'd just make sure that all of these 404s are intentional and none are valuable pages or occurring because of issues with the new CMS itself. It's easy to overlook something when you're talking about 100K pages, and it could be more than just a big chunk of 404s.

[Blenny]

Great stuff..thanks again for your advice..much appreciated!