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salam every one, this is a topic from google web master centrale blog: We see two kinds of 404 ("File not found") responses on the web: "hard 404s" and "soft 404s." We discourage the use of so-called "soft 404s" because they can be a confusing experience for users and search engines. Instead of returning a 404 response code for a non-existent URL, websites that serve "soft 404s" return a 200 response code. The content of the 200 response is often the homepage of the site, or an error page.

How does a soft 404 look to the user? Here's a mockup of a soft 404: This site returns a 200 response code and the site's homepage for URLs that don't exist.



As exemplified above, soft 404s are confusing for users, and furthermore search engines may spend much of their time crawling and indexing non-existent, often duplicative URLs on your site. This can negatively impact your site's crawl coverage—because of the time Googlebot spends on non-existent pages, your unique URLs may not be discovered as quickly or visited as frequently.

What should you do instead of returning a soft 404?
It's much better to return a 404 response code and clearly explain to users that the file wasn't found. This makes search engines and many users happy.

Return 404 response code



Return clear message to users



Can your webserver return 404, but send a helpful "Not found" message to the user?
Of course! More info as "404 week" continues!

Written by Maile Ohye, Developer Programs Tech Leadthis is a topic published in 2013... to get contents for your blog or your forum, just contact me at: devnasser@gmail.com

from web contents: Farewell to soft 404s 2013

salam every one, this is a topic from google web master centrale blog:
One of the things I'm thinking about in 2009 is how Google can be even more transparent and communicate more. That led me to a personal goal for 2009: if I give a substantial conference presentation (not just a question and answer session), I'd like to digitize the talk so that people who couldn't attend the conference can still watch the presentation.

In that spirit, here's a belated holiday present. In November 2008 I spoke on a panel about "Preventing Virtual Blight" at the Web 2.0 Summit in San Francisco. A few weeks later I ended up recreating the talk at the Googleplex and we recorded the video. In fact, this is a "director's cut" because I could take a little more time for the presentation. Here's the video of the presentation:



And if you'd like to follow along at home, I'll include the actual presentation as well:



You can also access the presentation directly. By the way thanks to Wysz for recording this not just on a shoestring budget but for free. I think we've got another video ready to go pretty soon, too.

Written by Matt Cutts, Search Quality Team
this is a topic published in 2013... to get contents for your blog or your forum, just contact me at: devnasser@gmail.com

from web contents: Preventing Virtual Blight: my presentation from Web 2.0 Summit 2013

salam every one, this is a topic from google web master centrale blog:
Carpe diem on any duplicate content worries: we now support a format that allows you to publicly specify your preferred version of a URL. If your site has identical or vastly similar content that's accessible through multiple URLs, this format provides you with more control over the URL returned in search results. It also helps to make sure that properties such as link popularity are consolidated to your preferred version.

Let's take our old example of a site selling Swedish fish. Imagine that your preferred version of the URL and its content looks like this:

http://www.example.com/product.php?item=swedish-fish


However, users (and Googlebot) can access Swedish fish through multiple (not as simple) URLs. Even if the key information on these URLs is the same as your preferred version, they may show slight content variations due to things like sort parameters or category navigation:

http://www.example.com/product.php?item=swedish-fish&category=gummy-candy

Or they have completely identical content, but with different URLs due to things such as a tracking parameters or a session ID:

http://www.example.com/product.php?item=swedish-fish&trackingid=1234&sessionid=5678

Now, you can simply add this <link> tag to specify your preferred version:

<link rel="canonical" href="http://www.example.com/product.php?item=swedish-fish" />

inside the <head> section of the duplicate content URLs:

http://www.example.com/product.php?item=swedish-fish&category=gummy-candy
http://www.example.com/product.php?item=swedish-fish&trackingid=1234&sessionid=5678

and Google will understand that the duplicates all refer to the canonical URL: http://www.example.com/product.php?item=swedish-fish. Additional URL properties, like PageRank and related signals, are transferred as well.

This standard can be adopted by any search engine when crawling and indexing your site.

Of course you may have more questions. Joachim Kupke, an engineer from our Indexing Team, is here to provide us with the answers:

Is rel="canonical" a hint or a directive?
It's a hint that we honor strongly. We'll take your preference into account, in conjunction with other signals, when calculating the most relevant page to display in search results.

Can I use a relative path to specify the canonical, such as <link rel="canonical" href="product.php?item=swedish-fish" />?
Yes, relative paths are recognized as expected with the <link> tag. Also, if you include a <base> link in your document, relative paths will resolve according to the base URL.

Is it okay if the canonical is not an exact duplicate of the content?
We allow slight differences, e.g., in the sort order of a table of products. We also recognize that we may crawl the canonical and the duplicate pages at different points in time, so we may occasionally see different versions of your content. All of that is okay with us.

What if the rel="canonical" returns a 404?
We'll continue to index your content and use a heuristic to find a canonical, but we recommend that you specify existent URLs as canonicals.

What if the rel="canonical" hasn't yet been indexed?
Like all public content on the web, we strive to discover and crawl a designated canonical URL quickly. As soon as we index it, we'll immediately reconsider the rel="canonical" hint.

Can rel="canonical" be a redirect?
Yes, you can specify a URL that redirects as a canonical URL. Google will then process the redirect as usual and try to index it.

What if I have contradictory rel="canonical" designations?
Our algorithm is lenient: We can follow canonical chains, but we strongly recommend that you update links to point to a single canonical page to ensure optimal canonicalization results.

Can this link tag be used to suggest a canonical URL on a completely different domain?
**Update on 12/17/2009: The answer is yes! We now support a cross-domain rel="canonical" link element.**

Previous answer below:
No. To migrate to a completely different domain, permanent (301) redirects are more appropriate. Google currently will take canonicalization suggestions into account across subdomains (or within a domain), but not across domains. So site owners can suggest www.example.com vs. example.com vs. help.example.com, but not example.com vs. example-widgets.com.

Sounds great—can I see a live example?
Yes, wikia.com helped us as a trusted tester. For example, you'll notice that the source code on the URL http://starwars.wikia.com/wiki/Nelvana_Limited specifies its rel="canonical" as: http://starwars.wikia.com/wiki/Nelvana.

The two URLs are nearly identical to each other, except that Nelvana_Limited, the first URL, contains a brief message near its heading. It's a good example of using this feature. With rel="canonical", properties of the two URLs are consolidated in our index and search results display wikia.com's intended version.

Feel free to ask additional questions in our comments below. And if you're unable to implement a canonical designation link, no worries; we'll still do our best to select a preferred version of your duplicate content URLs, and transfer linking properties, just as we did before.

Update: this link-tag is currently also supported by Ask.com, Microsoft Live Search and Yahoo!.

Update: for more information, please see our Help Center articles on canonicalization and rel=canonical.

Written by Joachim Kupke, Senior Software Engineer, and Maile Ohye, Developer Programs Tech Lead
this is a topic published in 2013... to get contents for your blog or your forum, just contact me at: devnasser@gmail.com

from web contents: Specify your canonical 2013

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