There could be several possiblities:
1) You don't have an items/show.php file in your theme directory. Check that you have this file in whatever theme you're using (look like the default theme).
2) You don't have an .htaccess file in the root of your installation. Make sure you have this.
3) You have an .htaccess file, but mod_rewrite isn't enabled on your server.
4) You have an .htaccess file at the /omeka/ root, and mod_rewrite is enabled, but you also have a .htaccess file at the root of your site (http://146.96.128.33/).
I suspect its either #2 or #3, because you can't get to http://146.96.128.33/omeka/items/browse or http://146.96.128.33/omeka/collections/browse, but you can get to your admin.
If you don't have a .htaccess file in your /omeka/ directory, be sure to upload the one included with the download.
If mod_rewrite is enabled, and you do have a .htaccess file in the root of your directory, then #4 is a possibility. In that case, try adding the RewriteBase to the .htaccess file, as detailed in this forum post.
If none of this works, let us know and we'll investigate further.
Best,
Jeremy