Hello. I was just trying to make a new post on my site (http://pressquare.com) when this error showed up.
Method Not Implemented
GET to /wp-admin/post.php not supported.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
I googled a little and there is a file called .htaccess involved. So, I went to the root of wordpress where is was supposed to be, but I found nothing, even when selecting the option "show hidden files". Then, I thought "well, if it doesn't exist then let's create one" and I did, many times, with different codes I found all over the Internet. The result? None of them worked, most of them did nothing and some even made the website crash.
This is the second time this happens, last time was months ago in a similar situation: making a post with a lot of content (video, featured image, tags, category, all kind of fonts, hyperlinks, etc)
So, how do I fix this? As you can guess, I have no relation with web development, so try to make the solution as simple as possible.