Dear Sir/Madam,
Please consider that as a cover letter.
Since most editors' task is to make a written work ready for publication, they mostly focus on the content of such work and not necessarily on the form and the grammatical structure of it. As a result, some errors might remain unnoticed. That is where the role of a proofreader begins.
As a professional proofreader, I will scan the entire written work (web-site, essay, brochure, newsletter, report, blog, email, and so forth…) for any possibly unnoticed errors. On the first read, I will pay more attention to fact checking, making sure names, places and objects are spelled consistently throughout the work. Closer attention must also be given to grammatical and word-usage errors, for instance, the use of verb tense, adverbs, adjectives, prepositions, parallel structure, dangling modifiers, misplaced modifiers, subject-verb agreement, subject reference, the use of quotes, bloc quotes, italics, numerals, headlines, titles and subtitles, hyphens, em-dashes and en-dashes, spaces, page layout, fonts, page-side margins, page numbers, images and captions (if any), reference citations (both in-text and list citations), indexes (if any), and so forth…The tool I usually use for online proofreading/copy-editing is Word Track Change option and Comment feature.
Best regards,
Mohamed Rachidi