Warning: add-on extensions can cause Firefox to malfunction. This afternoon and evening I spent hours trying to figure out why some CSS3 commands were not working and the vertical scroll bar was vanishing from websites every time I shrank the Firefox window to the width of 530px. I assumed I was pushing the scroll bar off the screen by use of some combination of CSS directives.

After spending hours trying to decide what CSS3 combinations I might have used to case a problem, I went searching the internet and found multiple users had found similar behavior, but, there did not appear to be a common thread. Each person seemed to have the problem in different combinations or configuration that used Firefox.

Finally, I found a website where a person indicated that she was having the problem and a helpful person indicated she should disable her add-ons and see if the problem went away. She did not respond to the comment. Allow me to answer. In my case, this solved my problem. By process of elimination, I found the culporate to be the extension “PHP Developer ToolBar 3.0.5” by FelipeNMoura.

My comment is not intended to complain about the add-on, Felipe Moura did make an effort to provide a service, and I thank him for the effort. The comment is intended to let all know that it is possible for Firefox to malfunction as the result of add-ons, and you should disable plugins if you appear to have some subtle problems as you debug your website behaviors.