Ever wonder about how Google handling the JavaScript on your site? It’s a common question, as Google’s Matt Cutts has discussed it several times in Webmaster Help videos.

Google took to its Webmaster Central blog on Friday to talk about it even more, and offer a bit of perspective about just how far it’s come when it comes to handling JavaScript since the early days when it basically didn’t handle it at all.

Beyond patting itself on the back though, Google offers some useful information – specifically things that may lead to a negative impact on search results for your site.

“If resources like JavaScript or CSS in separate files are blocked (say, with robots.txt) so that Googlebot can’t retrieve them, our indexing systems won’t be able to see your site like an average user,” the post, co-written by a trio of Googlers, says. “We recommend allowing Googlebot to retrieve JavaScript and CSS so that your content can be indexed better. This is especially important for mobile websites, where external resources like CSS and JavaScript help our algorithms understand that the pages are optimized for mobile.”

“If your web server is unable to handle the volume of crawl requests for resources, it may have a negative impact on our capability to render your pages. If you’d like to ensure that your pages can be rendered by Google, make sure your servers are able to handle crawl requests for resources,” the continues. “It’s always a good idea to have your site degrade gracefully. This will help users enjoy your content even if their browser doesn’t have compatible JavaScript implementations. It will also help visitors with JavaScript disabled or off, as well as search engines that can’t execute JavaScript yet.”

Google also notes that some JavaScript is too complex or arcane for it to execute, which means they won’t be able to render the page fully or accurately. That’s something to keep in mind for sure.

Also, some JavaScript removes content from the page, which prevents Google from indexing it.

Google says it’s working on a tool for helping webmasters better understand how Google renders their site, which will be available in Webmaster Tools within days.

Image via Google