image size conundrum

[Bullit]

ineresting:

I just copied and pasted a 57Kb image from the web and it pasted at a size of 120Kb (into irfanview)

I then right clicked the image in the browser and saved a copy at 57kb

why when i went the first way it inflated to 120kb? Looking closely at the images there is no difference

why is this?

 

[Hackerman]

all I can think is that it might have been pasted in a different format (different format= different compresion= larger or smaller size)