Google Webmaster Tools crawl error with 'function.session-start' URLs

Question

I've got following error URLs from the Google Webmaster Tools crawl errors.

http://www.mydomain.com/mydomain/shirts/function.session-start

I've checked the those pages that links from but I didn't found any wrong URL with function.session-start.

What is the issue there and how to avoid it?

Answer 1

Googlebot uses heuristics to parse your JavaScript for things that look like URLs. It then follows those URLs and when they are 404, it reports them in Webmaster Tools.

In my opinion, this is a bug. Googlebot shouldn't be reporting these in webmaster tools even when it does crawl them and find 404s. These aren't broken links on your site that you need to fix. It is annoying to webmasters that like to make sure that sites are problem free. These are presented as problems when they are not.

Here is what Google's John Mueller has to say about it (especially the third point):

1. 404 errors on invalid URLs do not harm your site’s indexing or ranking in any way. It doesn’t matter if there are 100 or 10 million, they won’t harm your site’s ranking. http://googlewebmastercentral.blogspot.ch/2011/05/do-404s-hurt-my-site.html
2. In some cases, crawl errors may come from a legitimate structural issue within your website or CMS. How you tell? Double-check the origin of the crawl error. If there's a broken link on your site, in your page's static HTML, then that's always worth fixing. (thanks +Martino Mosna)
3. What about the funky URLs that are “clearly broken?” When our algorithms like your site, they may try to find more great content on it, for example by trying to discover new URLs in JavaScript. If we try those “URLs” and find a 404, that’s great and expected. We just don’t want to miss anything important (insert overly-attached Googlebot meme here). http://support.google.com/webmasters/bin/answer.py?answer=1154698
4. You don’t need to fix crawl errors in Webmaster Tools. The “mark as fixed” feature is only to help you, if you want to keep track of your progress there; it does not change anything in our web-search pipeline, so feel free to ignore it if you don’t need it. http://support.google.com/webmasters/bin/answer.py?answer=2467403
5. We list crawl errors in Webmaster Tools by priority, which is based on several factors. If the first page of crawl errors is clearly irrelevant, you probably won’t find important crawl errors on further pages. http://googlewebmastercentral.blogspot.ch/2012/03/crawl-errors-next-generation.html
6. There’s no need to “fix” crawl errors on your website. Finding 404’s is normal and expected of a healthy, well-configured website. If you have an equivalent new URL, then redirecting to it is a good practice. Otherwise, you should not create fake content, you should not redirect to your homepage, you shouldn’t robots.txt disallow those URLs -- all of these things make it harder for us to recognize your site’s structure and process it properly. We call these “soft 404” errors. http://support.google.com/webmasters/bin/answer.py?answer=181708
7. Obviously - if these crawl errors are showing up for URLs that you care about, perhaps URLs in your Sitemap file, then that’s something you should take action on immediately. If Googlebot can’t crawl your important URLs, then they may get dropped from our search results, and users might not be able to access them either.

Answer 2

I once had the same problem, which I solved by adding the following lines to my .htaccess file:

php_flag display_startup_errors off
php_flag display_errors off
php_flag html_errors off

Also check that your php.ini is fine.