I'm so confused...

[wendy]

I was on your Web site, and you have some pictures and videos of you guys partying like ******* animals

Can I replace it with " your guys partying"?

You can't replace it with 'your' unless they belong to the person in some way.

This is one of those situations in which the possessive + gerund form doesn't work very well.

but

==> Well, yes, and no. Yes, if you want it to mean, 'just your friends partying', and no, if you want it to mean, 'you and the guys partying'.

I'm still confused. Can I replace it with "your guys partying"?

[Casiopea]

I was on your Web site, and you have some pictures and videos of you guys partying like ******* animals

Can I replace it with " your guys partying"?

You can't replace it with 'your' unless they belong to the person in some way.

This is one of those situations in which the possessive + gerund form doesn't work very well.

but

==> Well, yes, and no. Yes, if you want it to mean, 'just your friends partying', and no, if you want it to mean, 'you and the guys partying'.

I'm still confused. Can I replace it with "your guys partying"?

'you guys' means, you people (i.e. 'you' is plural). If we omit the word 'guys', like this,

1. pictures of you partying

the resulting meaning is singular 'you', like this,

2. pictures of you, John, partying.

The pictures are of one person only: John.

The word 'guys' is important because it tells us 'you' is plural, and not singular.

Next, if we change 'you' to 'your', like this,

3. pictures of your guys partying

the resulting meaning is the 'guys' belong to you. That is, your friends, they alone, were in the pictures; you weren't in the pictures.

If we change 'your' back to 'you', like this,

4. pictures of you guys partying

'partying' functions as a modifier. It describes what 'you guys' were doing in the pictures.

Consider the structure of the phrase:

5. pictures of you guys partying
Structure: pictures (that were taken) of people (doing something)

Participles generally answer the question "Doing what?", whereas gerunds answer the question "What?"

EX: Partying is fun.
Question: What is fun?
Answer: Partying. (Gerund)

EX: A partying animal
Question: An animal doing what?
Answer: Partying. (Participle)

EX: Pictures of you guys (Doing what?) partying. (Participle)

:D