Resize thumbs on different screen resolutions

Hi,

On this moment i working on the browny wind theme.
I will let it scale to the users screen resolution.
And that works (so far so good :P)

But now the problem:
I detect the users screen resolution and then i load the right css to give the width and height.
In this view mode it works perfect: http://mydigitalworld.nl/index.php/Maan/IMG_0322
I do that by the code:
#g-photo img {
width: auto;
max-width: 400px;
height: auto;
max-height: 300px;
}

By example the 400px and 300px is for the resolution 1360x768.

Now i will do the same by the thumbs.
Is there anyway to give some code (like above) that will do the same for thumbs?

Greets Kees.