How do I quote multiple posts? What is the Multi-Quote button?
To select a message to be quoted, click the Multi-Quote button. Note that the plus sign Multi-Quote changes to a minus sign -Quote which indicates that you have selected this post to quote. Click the Multi-Quote button to deselect it.
When at least one post has been selected for quoting, an Insert Quotes... button will appear below the reply text box.
Clicking the Insert Quotes... button will activate a pop-up window allowing you to confirm which of the selected posts you wish to quote in your reply. Select the required quoted posts and click the Quote These Messages button.
The posts will all be inserted into the reply box ready for you to add your comments.
For an in-depth explanation of Quoting See Here