difference - "some " vs. "some of "

Some of rules can be the same for most websites.

vs.

Some rules can be the same for most websites.

I think I want to say

Some of these rules can be the same for most websites.

Answer

The word some goes in the central determiner position. Other words that can go in this position are:

• a, the, my, no, any, either

We can only use one word in this position. If we want to use the words some, any either or numerals before another word in central determiner position, we can't. It's not grammatical:

• *any the people (ungrammatical)


• *some my friends (ungrammatical)


• *either the glasses (ungrammatical)


• *one my cats (ungrammatical)

In this situation we need to use any/some/either/one and the preposition of before the central determiner:

• any of the people



• some of my friends


• either of the glasses


• one of my cats

If there is no other word in central determiner position, we cannot use X of with a normal noun:

• *any of people (ungrammatical)


• *some of friends (ungrammatical)


• *any of glasses (ungrammatical)


• *one of cats (ungrammatical)

We just use the determiner on its own:

• any people


• some friends


• any glasses


• one cat

The original Poster's question:

1. 
   

   *Some of rules can be the same for most websites. (ungrammatical)

   
   


2. 
   

   Some rules can be the same for most websites.

   
   


3. 
   

   Some of these rules can be the same for most websites.

   
   

Sentence (1) is ungrammatical because there is no second determiner after the word of. Sentence (2) is grammatical, but it doesn't tell us which group of rules we are talking about. Sentence (3) is also grammatical. We know that the group of rules that can be the same is a subset of these rules. We don't know what these rules are without the context, but the sentence would be fine if we knew what the context was.