Hello,
I display 4 items/row in normal category .
I adapted the css but
for but for mobilephones I would like to display only 2 items for mobile display.


how can I test the width of screen on category.php ?

has anybody aready encountered the same problem ?

You can just override the width for smaller screens through the itemContainer class in your css. Locate the media query for smaller screens, in your template's css file, and add .itemContainer {width:50% !important;} for example.