If you're serious about your writing – and I mean any writing that is going to be seen by someone other than yourself – you should also be serious about getting your grammar right. This is the case even if you are of those who thinks grammar is overrated, that it's 'getting the meaning' that matters. Remember that a good proportion of your readers will baulk at any grammatical error and will quite possibly lose focus on what you're saying after they come across one.
In any case, good writing is professional writing. If you want to present yourself as someone who knows their stuff, you need to be able to write about that stuff in proper English.
So, next time you are wondering about the rights and wrongs of semicolons or dashes, where should you go for help?
While I have covered, and will continue to cover, grammatical issues from time to time, there are numerous excellent online resources dedicated to this task. Here are five websites I consult when finding myself in a lexicological knot.
Grammar Girl
Probably my first port of call because I find her explanations clear, thorough and entertaining. Grammar girl is the prolific Mignon Fogerty and sits within the quickanddirtytips.com portal. The site contains down-to-earth advice on nearly every grammatical challenge you might come across. She is American, so occasionally her advice can vary from what's 'acceptable' in British (or Australian) English. However, by-and-large she is at least aware of this and will often point out differences.
Oxford Dictionaries
The Oxford Dictionary has a nice clean website with a good grammar and usage section. There's also a good A-Z index on the site. The advice tends to be straight to the point (less chatty than Grammar Girl) but it is also highly cross referenced which can be useful when you're not quite sure what your question is. The advice here is, of course, coming from England so it is a good place to get a second opinion after visiting an American site.
Business Writing Blog
This is a blog more than a reference site, however its author, Lynn Gaertner-Johnston, has been writing for such a long time that her site is a virtual encyclopaedia on grammar and usage problems from a business angle. It is this perspective that makes the site particularly useful for business writing. Lynn covers a broad range of topics beyond just grammar, including etiquette. The same American-focused warning applies here as it does to Grammar Girl.
Daily Writing Tips
Another encyclopaedic blog, Daily Writing Tips makes you wonder if it will ever be possible to know everything there is about our language. The British site covers all manner of language challenges, and has a huge number of articles in its Grammar category. There's also a separate 'Grammar 101' category for 'learners'.
Online Grammar
For an Australian focus on matters grammatical, this site covers most of the ground you'll need to walk. Mary Morel's site is "based on her experiences as a teacher and business writing facilitator in the corporate world" and her explanations are mostly in answer to questions she's been asked along the way. They're brief and to the point, but they are also clear – and they come from an Australian perspective so there is lots of coverage of ambiguous spelling issues.
Most of these sites also have email newsletters attached to them that are worth subscribing to if you're interested in this sort of thing. Their authors are all well spread across social media as well. And of course if this lot doesn't provide you with enough information, just keep googling – there are hundreds of grammar and usage sites so at least one is bound to appeal.