So what's the catch? How much does this system cost?

Joomla! changes all that ...
Joomla! is different from the normal models for content management software. For a start, it's not complicated. Joomla! has been developed for everybody, and anybody can develop it further. It is designed to work (primarily) with other Open Source, free, software such as PHP, MySQL, and Apache.
It is easy to install and administer, and is reliable.
Joomla! doesn't even require the user or administrator of the system to know HTML to operate it once it's up and running.

Joomla! License Guidelines 
This Web site is powered by Joomla! The software and default templates on which it runs are Copyright 2005-2008 Open Source Matters. The sample content distributed with Joomla! is licensed under the Joomla! Electronic Documentation License. All data entered into this Web site and templates added after installation, are copyrighted by their respective copyright owners.
If you want to distribute, copy, or modify Joomla!, you are welcome to do so under the terms of the GNU General Public License. If you are unfamiliar with this license, you might want to read 'How To Apply These Terms To Your Program' and the 'GNU General Public License FAQ'.
The Joomla! licence has always been GPL

The Joomla! Community

Got a question? With more than 210,000 members, the Joomla! Discussion Forums at forum.joomla.org are a great resource for both new and experienced users. Ask your toughest questions the community is waiting to see what you'll do with your Joomla! site.
Do you want to show off your new Joomla! Web site? Visit the Site Showcase section of our forum.
Do you want to contribute?
If you think working with Joomla is fun, wait until you start working on it. We're passionate about helping Joomla users become contributors. There are many ways you can help Joomla's development:
Submit news about Joomla. We syndicate Joomla-related news on JoomlaConnectTM. If you have Joomla news that you would like to share with the community, find out how to get connected here. Report bugs and request features in our trackers. Please read Reporting Bugs, for details on how we like our bug reports served upSubmit patches for new and/or fixed behaviour. Please read Submitting Patches, for details on how to submit a patch.Join the developer forums and share your ideas for how to improve Joomla. We're always open to suggestions, although we're likely to be sceptical of large-scale suggestions without some code to back it up.Join any of the Joomla Working Groups and bring your personal expertise to the Joomla community. These are just a few ways you can contribute. See Contribute to Joomla for many more ways.

Content Layouts

Joomla! provides plenty of flexibility when displaying your Web content. Whether you are using Joomla! for a blog site, news or a Web site for a company, you'll find one or more content styles to showcase your information. You can also change the style of content dynamically depending on your preferences. Joomla! calls how a page is laid out a layout. Use the guide below to understand which layouts are available and how you might use them.
Content Joomla! makes it extremely easy to add and display content. All content is placed where your mainbody tag in your template is located. There are three main types of layouts available in Joomla! and all of them can be customised via parameters. The display and parameters are set in the Menu Item used to display the content your working on. You create these layouts by creating a Menu Item and choosing how you want the content to display.
Blog Layout
Blog layout will show a listing of all Articles of the selected blog type (Section or Category) in the mainbody position of your template. It will give you the standard title, and Intro of each Article in that particular Category and/or Section. You can customise this layout via the use of the Preferences and Parameters, (See Article Parameters) this is done from the Menu not the Section Manager!
Blog Archive Layout
A Blog Archive layout will give you a similar output of Articles as the normal Blog Display but will add, at the top, two drop down lists for month and year plus a search button to allow Users to search for all Archived Articles from a specific month and year.
List Layout
Table layout will simply give you a tabular list of all the titles in that particular Section or Category. No Intro text will be displayed just the titles. You can set how many titles will be displayed in this table by Parameters. The table layout will also provide a filter Section so that Users can reorder, filter, and set how many titles are listed on a single page (up to 50)
WrapperWrappers allow you to place stand alone applications and Third Party Web sites inside your Joomla! site. The content within a Wrapper appears within the primary content area defined by the "mainbody" tag and allows you to display their content as a part of your own site. A Wrapper will place an IFRAME into the content Section of your Web site and wrap your standard template navigation around it so it appears in the same way an Article would.
Content ParametersThe parameters for each layout type can be found on the right hand side of the editor boxes in the Menu Item configuration screen. The parameters available depend largely on what kind of layout you are configuring
 

Main menu

1.Article Index
2.Extensions 
3.Components 
4.Modules 
5.Plugins 
6.Languages 
7.All Pages 

Page 1 of 5Out of the box, Joomla! does a great job of managing the content needed to make your Web site sing. But for many people, the true power of Joomla! lies in the application framework that makes it possible for developers all around the world to create powerful add-ons that are called Extensions. An Extension is used to add capabilities to Joomla! that do not exist in the base core code. Here are just some examples of the hundreds of available Extensions:
Dynamic form builders Business or organisational directories Document management Image and multimedia galleries E-commerce and shopping cart engines Forums and chat software Calendars E-mail newsletters Data collection and reporting tools Banner advertising systems Paid subscription services and many, many, more You can find more examples over at our ever growing Joomla! Extensions Directory. Prepare to be amazed at the amount of exciting work produced by our active developer community!
A useful guide to the Extension site can be found at:
http://extensions.joomla.org/content/view/15/63/
Types of Extensions There are five types of extensions:
Components Modules Templates Plugins Languages You can read more about the specifics of these using the links in the Article Index - a Table of Contents (yet another useful feature of Joomla!) - at the top right or by clicking on the Next link below.

Example Pages and Menu Links

This page is an example of content that is Uncategorized; that is, it does not belong to any Section or Category. You will see there is a new Menu in the left column. It shows links to the same content presented in 4 different page layouts.
Section BlogSection TableBlog CategoryCategory TableFollow the links in the Example Pages Menu to see some of the options available to you to present all the different types of content included within the default installation of Joomla!.
This includes Components and individual Articles. These links or Menu Item Types (to give them their proper name) are all controlled from within the Menu Manager->[menuname]->Menu Items Manager.

Example of Section Blog layout (FAQ section)I installed with my own language, but the Back-end is still in English       
A lot of different languages are available for the Back-end, but by default this language may not be installed. If you want a translated Back-end, get your language pack and install it using the Extension Installer. After this, go to the Extensions Menu, select Language Manager and make your language the default one. Your Back-end will be translated immediately.
Users who have access rights to the Back-end may choose the language they prefer in their Personal Details parameters. This is of also true for the Front-end language.
A good place to find where to download your languages and localised versions of Joomla! is Translations for Joomla! on JED


Does the PDF icon render pictures and special characters? 
Yes! Prior to Joomla! 1.5, only the text values of an Article and only for ISO-8859-1 encoding was allowed in the PDF rendition. With the new PDF library in place, the complete Article including images is rendered and applied to the PDF. The PDF generator also handles the UTF-8 texts and can handle any character sets from any language. The appropriate fonts must be installed but this is done automatically during a language pack installation

How do I remove an Article?

To completely remove an Article, select the Articles that you want to delete and move them to the Trash. Next, open the Article Trash in the Content Menu and select the Articles you want to delete. After deleting an Article, it is no longer available as it has been deleted from the database and it is not possible to undo this operation.

What is an Uncategorised Article?       
Most Articles will be assigned to a Section and Category. In many cases, you might not know where you want it to appear so put the Article in the Uncategorized Section/Category. The Articles marked as Uncategorized are handled as static content
 

Where did the Mambots go?        

Mambots have been renamed as Plugins.
Mambots were introduced in Mambo and offered possibilities to add plug-in logic to your site mainly for the purpose of manipulating content. In Joomla! 1.5, Plugins will now have much broader capabilities than Mambots. Plugins are able to extend functionality at the framework layer as well
 

What is an Uncategorised Article?       
Most Articles will be assigned to a Section and Category. In many cases, you might not know where you want it to appear so put the Article in the Uncategorized Section/Category. The Articles marked as Uncategorized are handled as static content
 

How do I install Joomla! 1.5?

Installing of Joomla! 1.5 is pretty easy. We assume you have set-up your Web site, and it is accessible with your browser.

Download Joomla! 1.5, unzip it and upload/copy the files into the directory you Web site points to, fire up your browser and enter your Web site address and the installation will start.
For full details on the installation processes check out the Installation Manual on the Joomla! Help Site where you will also find download instructions for a PDF version too

Is it possible to change A Menu Item's Type?        

You indeed can change the Menu Item's Type to whatever you want, even after they have been created.
If, for instance, you want to change the Blog Section of a Menu link, go to the Control Panel->Menus Menu->[menuname]->Menu Item Manager and edit the Menu Item. Select the Change Type button and choose the new style of Menu Item Type from the available list. Thereafter, alter the Details and Parameters to reconfigure the display for the new selection as you require it

What are the requirements to run Joomla! 1.5?        

Joomla! runs on the PHP pre-processor. PHP comes in many flavours, for a lot of operating systems. Beside PHP you will need a Web server. Joomla! is optimized for the Apache Web server, but it can run on different Web servers like Microsoft IIS it just requires additional configuration of PHP and MySQL. Joomla! also depends on a database, for this currently you can only use MySQL.
Many people know from their own experience that it's not easy to install an Apache Web server and it gets harder if you want to add MySQL, PHP and Perl. XAMPP, WAMP, and MAMP are easy to install distributions containing Apache, MySQL, PHP and Perl for the Windows, Mac OSX and Linux operating systems. These packages are for localhost installations on non-public servers only.
The minimum version requirements are:
Apache 1.x or 2.xPHP 4.3 or upMySQL 3.23 or upFor the latest minimum requirements details, see Joomla! Technical Requirements