I came across a rather bizarre explanation of uncountable nouns on an ESL website specialising in grammatical explanations:
In English, Uncountable nouns only used in the singular tense.
My mother lost her keys.
The boys play ball all the time.
The grammatical mistake in the sentence about uncountable nouns could be a simple typing mistake; it's easy to miss out word when typing and type 'only used' instead of 'are only used'. It is much less easy to type 'singular tense' as these words are not collocations. However, to teach that 'keys' is an adjective in this sentence displays a shallow knowledge of grammar, which makes me wonder why this person has decided to set up a grammar help site. They must be unaware of just how flaky their knowledge is. Out of four examples in the adjectives after verbs section, two are wrong. This is not a lack of expertise; it's a lack of knowledge of the basics.
On another site, I came across this from a teacher looking for a job:
I can offer capacity to teach and ability to work effective and efficients with students.Intriguingly, this person claims to have four years' teaching experience at primary level, and also to be a native speaker. If this is the person's best shot, and it should be as it's meant to attract employers, then I can only hope that they are lying about their experience.
In both cases, there is a characteristic that is worrying; they have no idea of their own level of knowledge. One wants to get a job, blithely unaware that we don't put adjectives into the plural, and that we should be using an adverb there anyway, while the other is putting up grammar help about the 'singular tense'. Fortunately, the 'efficients' teacher is looking for employment and the grammar site is lurking in the bottom depths of the Alexa ranking. And long may they stay that way.