Ongoing front-end design for full-featured web app

Budget: $10,000 +

Innovative software company seeks a part-time Web designer with skills at graphic design, page layout, CSS, and HTML5, to create detailed user interface (UI) for a Web-based software application. We work via Internet, so you can be located anywhere. We expect to need about 8 to 16 hours per week for a year, though the exact amount of work can vary.
Our site (which is not yet public) involves complex user interaction with various controls, fields, widgets, etc. We have a basic design, but a lot of work is needed to improve and expand it. We are programmers and need your expertise as a designer and Web implementer.
For comparison, our site will eventually be about as complex as these examples:
https://c9.io/site/features/
http://www.quackit.com/html/online-html-editor/
http://www.campaignmonitor.com/features/

Qualifications we seek:- Experience making detailed designs (layouts, color schemes, etc.)- Experience designing detailed user interface elements (buttons, dialogs, shadow boxes, etc.)- Ability to implement your designs using drawing software, CSS, and HTML5- Experience implementing CSS and HTML that work properly across multiple browsers- Experience rapidly producing draft (prototype) designs using appropriate prototyping tools- Ability to test your work across multiple browsers, and to find and fix cross-browser bugs or compatibility issues- Good English language skills, in writing and by voice- Ability to quickly produce good-quality work with little supervision- Bonus points if you have deeper skills at usability, user interface (UI), or user experience (UX) design- Bonus points if you are familiar with the design of software development tools or similarly complex applications- Bonus points if you are also experienced at tablet (touch-oriented) user interface

Responsibilities:- Understand our needs by communicating via email, written specifications, Skype (voice), and our bug-tracking website- Produce mock-ups of detailed design proposals- Create HTML files and CSS files- Create simple image files, such as buttons and icons- Create and use color schemes, font schemes, layouts, and other graphic design standards for the site- Maintain and revise the work in response to feedback, expansion, and changing customer needs

Not required:- You don't need to be located in the USA. We work by Internet.- You don't need to be a programmer. We are programmers.
Compensation:We respect Web design as a valuable profession. You will be an independent contractor. Work from your own location using your own favorite software. We are estimating US $30 per hour. We do pay for time spent communicating with us, such as gathering requirements. Your work hours will be very flexible; you do need to be available to interact with us, get feedback, and turn around design changes or new features in a timely manner.