Writer with experience in writing computer tutorials and guides

Hello,
I need a writer with great command of the english language and a good knowledge about one or more of these topics:

Coding
Photoshop (with mandatory pictures)
Adobe products
SEO
Wordpress
HTML
Web developing

The writer will be hired to write guides and tutorials on demand, ranging from 250 to 1000 words.

The writer will not sign his articles, so he should forfeit all claims on them.

I will require a test article to evaluate the writer's skill. If rejected, this article will not be published anywhere or otherwise used. If accepted, the writer will get paid for it.

As this is my first job offer on OnlineJobs, i'm not quite sure what would be a fair rate. So, I will take online figures and round them up to PHP 100 for a 400-word tutorial (more if pictures are needed), scaling up or down with the amount of words.

I will not request more than one article every two or three days, so the job will not be time consuming, and thus ideal for students.

Thanks to all who will respond.