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In your div container place 
style=&quot;margin-right: auto; margin-left: auto; text-align: center;&quot; 
 
This is not necessarily the answsser, but it could be where you bgin. 
I strongly advise you do a little searching on the following text 
&nbsp; centering a div 
 
I hope this helps.
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I will note a couple things for you.. 
while its deprecated, you will still see in transitional (and even strict) markup the old 
align=&quot;center&quot; used in a div, typically for rearward compatibility with older browsers, but also sometimes to help overcome centering challenges none-the-less. &nbsp;I am not saying its recommended, only that you will still see it 'out there'. 
 
One of the contemporary methods is to us the margin left/right auto setting, however, the result will depend on several other things falling into place... 
&nbsp;- is the div occupying the full width of the page section its in 
&nbsp;- is it doing so, or not, in conjunction with, or not, cascading 'width' settings for its parent container ? 
 
How a container width style responds is connected to its relationship with its parent. 
I only mean to point it out ...so that you can be mindful to be looking for discussions on this sort of thing as you hunting out learning materials for gaining a proper over-view, which I think is beyond the scope here. 
 
Again, I hope this helps (a little more ;^). 

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<div class="content wysiwyg-content">
I need to center the green heading &lt;h1&gt; on line 12, but I am having trouble including both styles. &nbsp;Please advise if possible. 
 

<pre><code class="code-10 nolinks" id="code-8225539">&lt;!DOCTYPE html PUBLIC &quot;-//W3C//DTD XHTML 1.0 Transitional//EN&quot;

 &quot;http://www.w3.org/TR/xhtml11/DTD/xhtml11-transitional.dtd&quot;&gt;
 
&lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot; xml:lang=&quot;en&quot; lang=&quot;en&quot;&gt;
&lt;head&gt;
&lt;meta http-equiv=&quot;Content-Type&quot; content=&quot;text/html; charset=utf-8&quot; /&gt;

&lt;title&gt;Lab 3-1b&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div&gt;&lt;h1 style=&quot;color:green&quot;&gt;BEAUTIFUL BACKYARDS&lt;/h1&gt;&lt;/div&gt;
Beutiful Backyards is a new company in town, and we are eager to get your business. Please take some time to review our simple backyards.
&lt;/body&gt;
&lt;/html&gt;
</code></pre>
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I need to center the green heading <h1> on line 12, but I am having trouble including both styles. Please advise if possible.

Center H1

HTML (HyperText Markup Language) is the main markup language for creating web pages and other information to be displayed in a web browser, providing both the structure and content for what is sent from a web server through the use of tags. The current implementation of the HTML specification is HTML5.

HTML

Web development includes all aspects of presenting content on intranets and the Internet, including delivery development, protocols, languages and standards, server software, browser clients, databases and multimedia generation.