Create a Visualforce page without the standard Salesforce header and display an image using the Visualforce image component.
The page must be named 'DisplayImage'.
It must NOT display the standard Salesforce header.
It must use a Visualforce apex:image component to display this image - https://developer.salesforce.com/files/salesforce-developer-network-logo.png

<apex:page showHeader="false" title='DisplayImage'> 
    <apex:pageBlock >
        <apex:image url="https://developer.salesforce.com/files/salesforce-developer-network-logo.png"/>
    </apex:pageBlock> 
</apex:page>

Challenge Not yet complete... here's what's wrong: 
The 'DisplayImage' page was not found.

Hello All,
I am stuck in below trailhead chanllange
Create a Visualforce page that displays the first name of the logged-in user.

• The page must be named 'DisplayUserInfo'.
• The displayed user information must be generated dynamically from the logged-in user.

Here below is my code. Please help me to find the solution.
<apex:page>
{!$User.FirstName } {!$User.LastName } ({!$User.Username })
</apex:page>