You have been given some fantastic advice already. While sentence structure, punctuation, and phrasing are critical parts of good communication, what most great writers posses is a recognizable voice.
Start simple; deliver clean and sharp messages. Over time your voice will start to creep out, When it does embrace it and release your unique character in prose.
The best thing you can do for yourself is to learn to write with proper grammer. No online grammar check is going to be flawless–and often times they don’t recognize the difference between proper grammar and efficient, proper grammar. Do yourself a huge favor and read Strunk’s The Elements of Style. It will teach you something equally as important as grammar, and that is saying as much as you can in as few words as possible.
Hey!
A simple tip that might come in handy…stick to short sentences. Always works! When you can’t do that, jot down the points, thougts, expressions and then join them with appropriate conjunctions, that will help you keep a check on the tenses and the subject verb agreement.
Hope this helps! 
Hey check the following links. I think it will be helpful.
http://www.egpet.net/vb/t589.html
http://www.associatedcontent.com/article/9156/best_books_for_improving_grammar_and.html
at the very least run everything you post on your site through a spell checker.
the best place to learn to improve one’s grammar I think its in forums. like this one
There are some great tools out there that can help you improve your writing. Try searching for terms such as “seo copywriting tools”, “copywriting tools”, “grammar tools”, etc. You might find some blogs covering the subject. 
I think best way to go is learn the grammar through reading books >_>
Can anyone really write good English by reading grammar texts? That would be like trying to win Wimbledon by learning the rules of tennis.
Hi , not sure of any freeware available for your needs, google right writer , it is a good paid option.
Just a matter of practice. I can’t think of any software or whatsoever that caters to correcting your article…hmmmm, the grammar check with m.word is not that accurate though. I am not using any checker. I am relying solely on my skills…he he he
This is not a resource, but it is a method I tell my students when they are handing in work. Finish the work and leave it for a few days. Don’t even look at it. After a few days, take the resource and read it out loud. If it sounds right, then you are on a good track. The reason you wait a few days without reading it is simple. If you keep working at it nonstop, you will read what you want to read and miss some mistakes….causing you to miss obvious mistakes. This will help you catch them.
Try:
Some language tips
Some editing and revising tips
Basic advice on spell-checkers and [URL=“http://www.freewritingadvice.com/index_files/gramcheck.htm”]grammar checkers.
you may also start reading newspaper online.
visit bbc’s web site the educations section may be helpful for u
Visit different forums and learn English. you can easily learn english through forums
LOL. I have to say that again, LOL: Even the southern intonation has its place I think. Someone up there said; “If you can talk, you can write” and this is so true - depending of course on whether you are talking to people who speak your language.
Where I come from, mis-understood writing boils down to; “WassumattaU”.
Always,
Phil
I do NOT recommend this way of learning English. In forums, there is so many people like me who are not native speakers. And if you will learn English from people like me, save you God
I used to read what I had written out loud, but now I use text-to-speech software. Sometimes your mind inserts the proper word rather than what you really have written. Text-to-speech software doesn’t make that mistake.