Hello I'm new to Salesforce and I'm doing the trailhead to learn.
But I'm stuck at this challenge in Lightning Module.

Here's the challenge:
Create a simple Lightning component with a styled headline. The headline must use an H1 tag with a CSS class that enforces a 24px font-size. Make the component available in the Navigation Menu of Salesforce1.The component must be named 'MyLightningComponent'.
The component must include an H1 tag with a CSS class named 'headline'. The 'headline' CSS class must set a font-size of 24px.
The Lightning Component tab that is added to Salesforce1 must be called 'MyLightning'.

And here's what I did:

MyLightningComponent.cmp

<aura:component implements='force:appHostable'>
    <div class="headline">
    <h1>My Lightning Component</h1>
    </div>
</aura:component>

MyLightningComponentApp.app

<aura:application>
    <h1>Hello Lightning App!</h1>
    <c:MyLightningComponent />
</aura:application>

MyLightningComponent.css

.THIS {
}

.THIS.headline{
    font-size:24px;
}

I created the tabs in the Salesforce1 and everithing looks right but I can't pass the challenge because it's aways return a error saying "The component does not include an H1 tag with a 'headline' CSS class"

I do no what to do with this error.

Hi,

We need to implement document preview in visualforce. the document may be image, pdf,ppt,word.
This is similar to chatter file previewer. I have gone through some hacks in salesforce,but if salesforce changes might reflect the functionality in future.

Any inputs or code samples are highly appreciated. Thank you

Anyone know how to put a content Previewer on Visualforce page?