Hi all, I am working on the Insecure Remote Site Trailhead and can't seem to get the image to display from a static resource zip file.

I am using this as my code
 

<apex:image url="{!URLFOR($Resource.Challenge_Resources,'Challenge_resources/Castle.png')}" />

Are there any steps I should take, hope it helps.

Is salesforce pardot is available for developers free of cost ? If not is there any trial option to explore the pardot as a product?