Downaload

Try using different browsers - so if you're using Chrome try IE or Firefox. 

Also, you must be downloading it from the Sims 3 website not Origin. It's a world not a game.

Did not work

So what happens ? Any error messages ?

See if this guide helps you: http://answers.ea.com/t5/The-Sims-3-Store/Guide-Sims-3-Store-Worlds/m-p/1589911