Popup message overriding the current browser page

I am using Ruby on Rails 3.0.9 and I would like to show a block (that is, something like a popup message - I think it should be a HTML div tag...) in the middle of a page without open a new page.

For example, clicking a link in a page it should appear overriding the current browser page and should have a fixed width. In few words, I would like开发者_运维知识库 to implement something as a Facebook "generic dialog popup".

How can I implement that? How I must state HTML and CSS?

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There are many, many solutions to modal dialogs in JS.

For example:

• http://ssssnakes.com/smoke/
• http://jqueryui.com/demos/dialog/
• http://onehackoranother.com/projects/jquery/boxy/