I was working with a custom Magento module. I had to display TinyMCE editor in an admin form field.
I was getting this error when I try to add/edit data from the custom module:-
Warning: Invalid argument supplied for foreach() in lib\Varien\Data\Form\Element\Editor.php on line 225

Here are some ubuntu linux commands to add and remove repository/software sources and applications.
Add application
sudo apt-get install {package-name}

Getting customers to your eCommerce store and making a purchase is one set of problems. Getting them to make repeated purchases, and maintaining their level of satisfaction with your company is a different set of problems.
Customer support is not easy to get right, as we’ve seen recently with Google’s apparent eCommerce incompetence with its constantly sold out Nexus products and badly malfunctioning shopping interface.

Here is a quick tip to change the landing or startup page of Magento Admin. I mean to say, when you login to Magento Admin, you land up on Dashboard page. You can change it to any page you like.
For example, you might want to see Orders page (Sales -> Orders) just after you login to Magento admin instead of the Dashboard page.