If in one homepage, I click 2 links sequentially in a fast way, what the results will be?

If in one homepage, I click 2 links sequentially in a fast way, what the results will be?

I find different homepage process this situation in different ways.

For some websites, if I click link A, then link B in a timely, the link B will show up. But if I click link B a little slower, then link A will show up.

For some websites, the first link clicked always shows up.

I am new to web. Any explanation and knowledge links would be appreciated.