I am returning to Prague soon and would like to know if it is advisable to purchase the Castle ticket online in advance or better to get it the morning of actual visit?
If you are at the Castle at opening time it's quite easy to get tickets. Remember, they are good for TWO days, so if you have the time there is no need to rush through the complex
If you can print your ticket then you have the option of doing this online. If you cannot print then buy on the day. Note if you buy on the day and you want a senior ticket you'll need to show proof of age.
When are you going? I hoped to tour the castle on Sept. 8 and the website shows no tickets are available from about Sept 5 - 30th. Drats. I think it is closed for a showing of the Crown Jewels?