Opening zip files usually require downloading the whole archive and then decompressing it using a software. Things get even more inconvenient if there are a couple of corrupted files in the archive or if you only need one file from the archive but have to download the whole thing to get to that file.
ArchView is a Firefox Add-on that allows you to preview zip files online without even downloading them. Supported compressed formats are .rar and .zip. You can even use ArchView to preview .iso files. Once you have installed the add-on, clicking on any zip file would open it just like a windows explorer window and show the the content of the zip file.
It is a very useful tool to preview the contents of the zip file and save yourself from the hassle of downloading it every time. It supports HTTP, FTP and other file protocols.