Is H1 Tag That's Hidden Using Display:None Given Prominence by Search Engines

CSS hidden text illegal for Search Engines?

You will find Google themselves actually use display:none; on their homepage - and considering the popularity of jQuery and other JavaScript libraries using these kinds of effects, I can't see how it will negatively impact your SEO if you use it in necessary circumstances.

Will search engines penalise text hidden by javascript?

Search engines are concerned about spamming. They have complex algorithms to detect various spamming techniques, such as stuffing a page with keywords which are then hidden by some means.

In your case the content is a perfectly legitimate part of the page, which is then manipulated by JavaScript. Even if search engines were able to detect that the text was being concealed by scripting, it would still not come under the category of spamming, and would not be penalised.

There's a lot of rubbish talked about this subject, much of it based on endlessly-recycled speculation by unknowledgeable people, usually traceable back to some article from seven or eight years ago that isn't even really relevant anymore (and was probably written by a spammer complaining about getting caught). The technique you are using is perfectly OK, and will not damage your site's ranking.

Hidden div content, do search engines consider this content or ignore it?

It will be indexed but can be frowned upon by Google if you are hiding/showing content for SEO reasons. In other words, what Google sees should be what the user sees when clicking the link.

have a look on this discussion at google form:

http://groups.google.com/group/Google_Webmaster_Help-Indexing/browse_thread/thread/fd91a80997e531b2/e0fe0c574aa44b8d?lnk=gst&q&pli=1

https://support.google.com/webmasters/answer/66355?hl=en

Hope this helps.

How to tell search engines which is the main menu?

it is right every page must have only one h1 and you may use h2 h3 and arrange your data for search engine

all links will be followed and archived in search engine by default except if you tell other by your robot meta tag in every page and not only the main one

you may submit sitemap xml in your website and search engine will submit all your pages.

my advice is to think in search engines in every page with it's content not the whole website, search engines archive and rank website pages, so the good pages friendly to search engine will appear in first results in searching about a content in this pages.

My Regards

Slideshow content's SEO development

Search engines see whatever you put in your HTML. Even if the content is hidden by CSS it is crawled and indexed by them.

How do I tell search engines about my flash content?

Lately google introduced indexing swf text content, and maybe other engines will follow.
For details see http://googlewebmastercentral.blogspot.com/2008/06/improved-flash-indexing.html