That's strange. When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

You also can clear Firefox's cache completely using:

"3-bar" menu button (or Firefox menu) > Preferences > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the globe or padlock in the address bar > More Information > "View Cookies"

The dialog that opens should show yoox.com at the top and list the cookies the site has set in your Firefox. You can remove them individually.

Then try reloading the page. Does that help?

Also, can you access your account on the site in Safari or Chrome to confirm it's just a problem in Firefox?