I am not a developer and try to make it as simple as possible for business people as well, so if you are not a developer as well keep reading and make sure you talk to your developer to take care of this. I have been asked this question a lot lately since one of the trends in webdesign in 2014 and 15 was to hide content on some pictures of frames or buttons and only show them when mouse hovers over the picture. The question is, does Google see these content and index them? The answer is yes and no. Short answer: If you wrap your text in HTML not Java or CSS, Google sees it. On the other hand Java/CSS codes are not that visible to Google yet, so it might not index them. Longer answer: Each developer as her/his own style for achieving things, one might prefer CSS over Java and vice versa. Google hates spams and spammy looking content. Google considers hidden content as spam on a website and if you have a ton of hidden content on your website Google does see that as spam and you might even pay a price for that. Although the new algorithm works much better but still very difficult to identify hidden content. So some SEO specialists suggest to use Java instead of CSS so you can use focus rather than hidden content. I suggest to consider having your most important keywords and content in HTML and do not risk it until Google finds a solution or a suggestion for it. A test by Mathew Edgar in Moz showed that Google was able to see and index document write method but had difficulty indexing Ajax tabs which refer to external files. Hope this helps some of you