jb42 on "[Plugin: Contact Form 7] Textarea width impossible to change"

Hello,

I'm having an issue with a textarea component.
I want it to be small in height (lets say 4 lines) and quite big in width (about 100 chars).

Here is my code :
[textarea your-message 100x4 placeholder "Entrez votre message ici"]

The problem is the 100x4.
If I understand, it must represent the size (colsxrows).
I can put anything like 2x4 or 200x4, the result is the same (the number of lines is working).

You can see it here

Do I do something wrong ?

Thanks

http://wordpress.org/extend/plugins/contact-form-7/