Its simple to fix Menu items opening a 404 Page Not Found error in joomla, just follow the following steps,

•     Open your configuration.php file and edit the var $live_site = ' '; line to match the actual URL of your website. If your website is http://yourdomain.com for example, the line should look like this:
•     var $live_site = 'http://www.yourdomain.com ';

While accessing your joomla site it occurs Database Error: Unable to connect to the database: Could not connect to database, the solution is simple...Check the following steps

It's very common purpose when it comes to insert advertising scripts
or other html codes in a joomla article.you can easily create a plugin
which can insert your code after title or content or before content
of the article.Following way i demonstrate how to achieve
this great task -

It's a very common to get joomla module's setting parameters in
code to process the module.It's easy but sometimes things
become complicated if you don't find the right way to do
that.

how to insert data in specific joomla table? this way -

session is a essential part of joomla. It's main use
is for remembering user login, also there are many
usage of it.