A. I'm betting you recently installed a free program, Catherine. Sometimes, free software includes pesky add-on programs, like browser toolbars.
Usually, you can choose not to install these extras during the program installation. However, if you just rushed through the install screens, you might have missed it.
Babylon is one of the more notorious programs of this type. It's a translation program that boasts 100 million downloads on its site. I wonder how many of those come from people not paying attention when installing programs.
I've tackled removing annoying programs like this in the past. However, some programs like Babylon will change your browser's settings in bizarre ways.
You didn't mention what browser you use, so I'll cover Firefox, Chrome or Internet Explorer. Safari users haven't reported Babylon being a problem, so we'll ignore it for now.