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salam every one, this is a topic from google web master centrale blog: Posted by John Blackburn, Webmaster Tools and Matt Dougherty, Search Quality

We've improved Webmaster Central's robots.txt analysis tool to recognize Sitemap declarations and relative URLs. Earlier versions weren't aware of Sitemaps at all, and understood only absolute URLs; anything else was reported as Syntax not understood. The improved version now tells you whether your Sitemap's URL and scope are valid. You can also test against relative URLs with a lot less typing.

Reporting is better, too. You'll now be told of multiple problems per line if they exist, unlike earlier versions which only reported the first problem encountered. And we've made other general improvements to analysis and validation.

Imagine that you're responsible for the domain www.example.com and you want search engines to index everything on your site, except for your /images folder. You also want to make sure your Sitemap gets noticed, so you save the following as your robots.txt file:

disalow images

user-agent: *
Disallow:

sitemap: http://www.example.com/sitemap.xml

You visit Webmaster Central to test your site against the robots.txt analysis tool using these two test URLs:

http://www.example.com
/archives

Earlier versions of the tool would have reported this:



The improved version tells you more about that robots.txt file:





We also want to make sure you've heard about the new unavailable_after meta tag announced by Dan Crow on the Official Google Blog a few weeks ago. This allows for a more dynamic relationship between your site and Googlebot. Just think, with www.example.com, any time you have a temporarily available news story or limited offer sale or promotion page, you can specify the exact date and time you want specific pages to stop being crawled and indexed.

Let's assume you're running a promotion that expires at the end of 2007. In the headers of page www.example.com/2007promotion.html, you would use the following:

<META NAME="GOOGLEBOT"
CONTENT="unavailable_after: 31-Dec-2007 23:59:59 EST">

The second exciting news: the new X-Robots-Tag directive, which adds Robots Exclusion Protocol (REP) META tag support for non-HTML pages! Finally, you can have the same control over your videos, spreadsheets, and other indexed file types. Using the example above, let's say your promotion page is in PDF format. For www.example.com/2007promotion.pdf, you would use the following:

X-Robots-Tag: unavailable_after: 31 Dec
2007 23:59:59 EST

Remember, REP meta tags can be useful for implementing noarchive, nosnippet, and now unavailable_after tags for page-level instruction, as opposed to robots.txt, which is controlled at the domain root. We get requests from bloggers and webmasters for these features, so enjoy. If you have other suggestions, keep them coming. Any questions? Please ask them in the Webmaster Help Group.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: New robots.txt feature and REP Meta Tags 2013

Seo Master present to you:

JavaScript libraries let developers do more with less code. But JavaScript libraries need to work on a variety of browsers, so using them often means shipping even more code. If JQuery has code to support XMLHttpRequest over ActiveX on an older browser like IE6 then you end up shipping that code even if your application doesn't support IE6. Not only that, but you ship that code to the other 90% of newer browsers that don't need it.


This problem is only going to get worse. Browsers are rushing to implement HTML5 and EcmaScript5 features like JSON.parse that used to be provided only in library code, but libraries will likely have to keep that code for years if not decades to support older browsers.


Lots of compilers (incl. (JSMin, Dojo, YUI, Closure, Caja) remove unnecessary code from JavaScript to make the code you ship smaller. They seem like a natural place to address this problems. Optimization is just taking into account the context that code is going to run in to improve it; giving compilers information about browsers will help them avoid shipping code to support marginal browsers to modern browsers.

The JavaScript Knowledge Base (JSKB) on browserscope.org seeks to systematically capture this information in a way that compilers can use.

It collects facts about browsers using JavaScript snippet. The JavaScript code (!!window.JSON && typeof window.JSON.stringify === 'function') is true if JSON is defined. JSKB knows that this is true for Firefox 3.5 but not Netscape 2.0.

Caja Web Tools includes a code optimizer that uses these facts. If it sees code like

if (typeof JSON.stringify !== 'function') { /* lots of code */ }

it knows that the body will never be executed on Firefox 3.5, and can optimize it out. The key here is that the developer writes feature tests, not version tests, and as browsers roll out new features, JSKB captures that information, letting compilers produce smaller code for that browser.


The Caja team just released Caja Web Tools, which already uses JSKB to optimize code. We hope that other JavaScript compilers will adopt these techniques. If you're working on a JavaScript optimizer, take a look at our JSON APIs to get an idea of what the JSKB contains.


If you're writing JavaScript library code or application code then the JSKB documentation can suggest good feature tests. And the examples in the Caja Web Tools testbed are good starting places.


By Mike Samuel (Caja), Lindsey Simon (Browserscope)

2013, By: Seo Master

seo Reversing Code Bloat with the JavaScript Knowledge Base 2013

salam every one, this is a topic from google web master centrale blog: Webmaster level: Intermediate

We've recently discussed several ways of handling duplicate content on a single website; today we'll look at ways of handling similar duplication across different websites, across different domains. For some sites, there are legitimate reasons to duplicate content across different websites — for instance, to migrate to a new domain name using a web server that cannot create server-side redirects. To help with issues that arise on such sites, we're announcing our support of the cross-domain rel="canonical" link element.



Ways of handling cross-domain content duplication:
  • Choose your preferred domain
    When confronted with duplicate content, search engines will generally take one version and filter the others out. This can also happen when multiple domain names are involved, so while search engines are generally pretty good at choosing something reasonable, many webmasters prefer to make that decision themselves.
  • Enable crawling and use 301 (permanent) redirects where possible
    Where possible, the most important step is often to use appropriate 301 redirects. These redirects send visitors and search engine crawlers to your preferred domain and make it very clear which URL should be indexed. This is generally the preferred method as it gives clear guidance to everyone who accesses the content. Keep in mind that in order for search engine crawlers to discover these redirects, none of the URLs in the redirect chain can be disallowed via a robots.txt file. Don't forget to handle your www / non-www preference with appropriate redirects and in Webmaster Tools.
  • Use the cross-domain rel="canonical" link element
    There are situations where it's not easily possible to set up redirects. This could be the case when you need to move your website from a server that does not feature server-side redirects. In a situation like this, you can use the rel="canonical" link element across domains to specify the exact URL of whichever domain is preferred for indexing. While the rel="canonical" link element is seen as a hint and not an absolute directive, we do try to follow it where possible.


Still have questions?

Q: Do the pages have to be identical?
A: No, but they should be similar. Slight differences are fine.

Q: For technical reasons I can't include a 1:1 mapping for the URLs on my sites. Can I just point the rel="canonical" at the homepage of my preferred site?
A: No; this could result in problems. A mapping from old URL to new URL for each URL on the old site is the best way to use rel="canonical".

Q: I'm offering my content / product descriptions for syndication. Do my publishers need to use rel="canonical"?
A: We leave this up to you and your publishers. If the content is similar enough, it might make sense to use rel="canonical", if both parties agree.

Q: My server can't do a 301 (permanent) redirect. Can I use rel="canonical" to move my site?
A: If it's at all possible, you should work with your webhost or web server to do a 301 redirect. Keep in mind that we treat rel="canonical" as a hint, and other search engines may handle it differently. But if a 301 redirect is impossible for some reason, then a rel="canonical" may work for you. For more information, see our guidelines on moving your site.

Q: Should I use a noindex robots meta tag on pages with a rel="canonical" link element?
A: No, since those pages would not be equivalent with regards to indexing - one would be allowed while the other would be blocked. Additionally, it's important that these pages are not disallowed from crawling through a robots.txt file, otherwise search engine crawlers will not be able to discover the rel="canonical" link element.

We hope this makes it easier for you to handle duplicate content in a user-friendly way. Are there still places where you feel that duplicate content is causing your sites problems? Let us know in the Webmaster Help Forum!


Posted by , Webmaster Trends Analyst, Google Zürichthis 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: Handling legitimate cross-domain content duplication 2013

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