KP, I'm sorry, but I'd like to interfere :) I didn't actually get what exactly you meant, but your comment made me think on the subject once again. And I believe when talking about ЕСЛИ and ЛИ, it's very important not to translate them, but to distinguish the situations where they are used. If we're talking about conditions or dreams, we use ЕСЛИ:

- Если у меня будет много денег, я куплю большой дом.

- Эх, если бы у меня было много денег...

On the other hand, ЛИ is used in reported questions without a question word and also in some direct questions (mostly in spoken Russian, and ЛИ is a a kind of auxiliary in this case):

- "У тебя есть деньги?" - спросил Андрей. --> Андрей спросил, есть ли у меня деньги.

- Есть ли у тебя деньги? Работа?

- Можно ли жить без денег? Много ли денег надо для счастья?

And the important thing about the position of ЛИ is that it goes AFTER the word the question/sentence is about (it's very often a verb, but not always). Compare the following examples:

- Все любят деньги. --> Я думаю, а все ЛИ любят деньги (или не все).

- Я получила деньги вчера?--> А вчера ЛИ я получила деньги (или в другой день).

Mileena, I didn't want to intrude, but just couldn't help it :)

Oh yes, the first 2 are omnnipresent!! And not just among the English speakers, it's widely common among the French and the Chinese as well (the latter mostly borrow the structure form English that they studied as a foreign language).

Unfortunately I don't collect mistakes, but the one which always grabs my attention is "покупить" or "куплять" instead of "покупать/купить". For instance:

- Вчера я покупил новую книгу. (instead of купил)

Valeriia, thanks for another explanation.

But it doesn't mean that explanation in the article is not correct.

Также и тоже can't have completely different meanings because they are interchangeable in some cases. 

Thank goodness you stopped at 4, it would have been too depressing! ;-) I think I have been guilty of 3 out of the 4! 

It does show the value of getting feedback from teachers though. Although I frequently realise my mistakes the moment I make them, or when I re-read my writing, there are always blind spots.

I think also that perhaps reading translated text can also help, in my case this means English to Russian flashcards. Not that long ago I found myself thinking: hmmm why is 'also' sometimes translated as 'тоже' and sometimes 'также'. I then did some research and found the rule you've described, and my rehabilitation began.

It's also not perhaps something to worry too much about. I find often that I begin to pick things up just from reading and listening without any study and start to use them tentatively and often incorrectly. Then later either by encountering it in a textbook, or by the process of discovery I described above, I come to understand the word or construction fully. Then I can work on it, and the mistakes will disappear sooner or later.

About также / тоже.

I couldn't say that the number of subjects is the point.

Также / тоже are used interchangeably when you talk about IDENTICAL actions, conditions etc.:

Я бросил курить, вам тоже/также нужно это сделать (=I quit smoking and you should do the same)
Я преподаватель и она также/тоже преподаватель (=We both are teachers, we do the same thing)

When you talk about SIMULTANEOUS actions or processes (taking place at the same time) or two COMPLEMENTARY actions/objects, then также is used:

Она говорит по-английски, а также учит китайский (=She speaks English and also / at the same time she learns Chinese)
Вам нужно прочитать первое, второе, а также третье предложение (= you need to read first, second and also / in addition to them third sentence).