Yes, Amiga browsers support JavaScript. iBrowse v2.3 has the best support right now. However, you shouldn't need it anyway. If a user loads the thumbnails page and then clicks on one of them, fast reloading of the entire page of thumbnails plus the big picture should be automatic. If the thumbnail URLs don't change, the browser's cache should load the images from disk or RAM rather than redownloading them from the net. If that's still not what you want, then JavaScript would be the way to go because PHP is on the server side and the whole page would likely have to be re-downloaded anyway.
