I've read some similar questions but the mine is about a particular case.
I need to hide the "main page content" as default, visible on user's request using javascript. This is lot of text - about 500-1000 words for every document.
The secondary page content (schematic data, lists, images) will be visible as default.
That's the solution that fits the needs of my customer.
Will a site made like this be penalized?
EDIT: The "main body text" is the text that should appear in search engine's results and it contains the keywords.