I just saw the Severe health issues are found on your site. Is robots.txt blocking important pages? message on Google Webmaster Tools.This is what I have in robots.txt:User-agent: *Allow: /*?p=Allow: /index.php/blog/Allow: /catalog/seo_sitemap/category/Allow: /catalogsearch/result/Allow: /media/Disallow: /404/Disallow: /app/Disallow: /cgi-bin/Disallow: /downloader/Disallow: /errors/Disallow: /includes/Disallow: /js/Disallow: /lib/Disallow: /magento/Disallow: /pkginfo/Disallow: /report/Disallow: /scripts/Disallow: /shell/Disallow: /skin/Disallow: /stats/Disallow: /var/Disallow: /contents/Disallow: /contents/fr/Disallow: /index.php/Disallow: /catalog/product_compare/Disallow: /catalog/category/view/Disallow: /catalog/product/view/Disallow: /catalogsearch/Disallow: /checkout/Disallow: /control/Disallow: /contacts/Disallow: /customer/Disallow: /customize/Disallow: /newsletter/Disallow: /poll/Disallow: /review/Disallow: /sendfriend/Disallow: /tag/Disallow: /wishlist/Disallow: /admin/Disallow: /cron.phpDisallow: /cron.shDisallow: /error_logDisallow: /install.phpDisallow: /LICENSE.htmlDisallow: /LICENSE.txtDisallow: /LICENSE_AFL.txtDisallow: /STATUS.txtDisallow: /*.js$Disallow: /*.css$Disallow: /*.php$Disallow: /*?p=*&Disallow: /*?SID= Disallow: /*?limit=allI copied this from Magento's default robots.txt and I added some folders that don't need to be indexed.
Google Webmaster Tool: Severe health issues are found on your site
web crawlers;robots.txt;magento
Google gives you that message when it finds out that many pages on your site that it had been indexing are now all blocked in robots.txt.    Whether or not that message is legitimate for you depends on whether you actually want those blocked pages crawled.  I'm not specifically familiar with Magento, but the following blocked URLs seem like they might contain important content that you want indexed in search engines:Disallow: /contents/Disallow: /catalog/category/view/Disallow: /catalog/product/view/Disallow: /newsletter/In addition to checking that those aren't disallowed by mistake you should:Run a site:example.com search on Google and see what they have indexed.  Check to make sure there isn't anything important that is now blocked by robots.txtExamine the URLs in your sitemap.   Nothing in your sitemap should be blocked by robots.txtUse Google Webmaster Tool's Fetch as Google tool to make sure that they can actually download some URLs that shouldn't be blocked.I would advise against disallowing the crawling of all JavaScript and CSS files.   You should remove the Disallow: /*.js$ and Disallow: /*.css$.   Google has said that they really want to be able to render your pages.   They do so for screenshot as well and ranking purposes.   Your site may not rank as well if they can't do this.