I am having the same issue as the above. I want to be able to widen all categories. I have tried all of the above suggestions to no avail. Unfortunately I am not that familiar with CSS. I know where to find the CSS Style Sheet by using the Editor under Appearance.
I have been copying the above suggestions at the very bottom of the CSS Style Sheet. I am using iFeature Pro 5 as my theme and Contact Form 7. Here is the URL link to my Contact / Booking page: http://trials2triumph.org/blog/contact-booking/. Thank you for your assistance!