Quick and Dirty Tips in English writing: Grammar Girl

I have learned English grammar since middle school and have not much difficulty in communicating in English.  But, as a non-native English speaker, I have always troubled with writing something official in English.  I often encounter delicate usage issues.  I have received some help from Grammar Girl, even though it does not cover every issue in detail.  When we have spare time, it is worthwhile to skim the website because it provides short and quick tips about English writing.

http://grammar.quickanddirtytips.com/