Can&#39;t get meaning from absence of notice of copyright symbol
<p>here i am starting writing blog post and i am totally new,i am using some contents from online power point presentation which don't have any copyright notice on it so is there any copyright infringement issues</p>

<p>What it means if the documents not contain © symbol and are posted in public domain have no grounds for violating copyright</p>

<p><a href="https://i.stack.imgur.com/UWCXP.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UWCXP.jpg" alt="enter image description here"></a></p>

<p>The text in the image means,</p>

<blockquote>
  <p>For works published after 1989, a copyright notice is not required for a work to enjoy copyright protection. If you use an unmarked work in a way that violates copyright, you cannot defend your use by claiming that the unmarked work is not under copyright.</p>
</blockquote>

<p>In most nations, all creative works are automatically under copyright per the Berne Convention. Prior to widespread adoption of the Berne Convention, authors needed to explicitly write a copyright notice on each work to make it covered under copyright.</p>

<p>A notable example of such a failure to mark a work is <a href="https://www.plagiarismtoday.com/2011/10/10/how-a-copyright-mistake-created-the-modern-zombie/" rel="nofollow"><em>Night of the Living Dead</em></a> published in 1968, which did not include correct copyright markings and became part of the public domain immediately. Such an event can no longer happen under modern copyright laws, since copyright now applies by default, not because of a marking.</p>

<p>The only effect copyright markings have in modern use is on innocent infringement. If you infringe a modern work the doesn't have copyright markings, you still infringe copyright, but you may be able to reduce the penalty by claiming that you didn't <em>know</em> copyright applied to the work. If the author includes a copyright notice, then you cannot claim ignorance of copyright.</p>

<p>It means that just because someone didn't put the copyright sign into a work, or didn't add a copyright notice, that doesn't give you any right to copy their work without a license, and doing so is still a violation of copyright law, and you mustn't do so. </p>

<p>It's expressed in a clumsy way. Obviously you must <em>never</em> violate copyright law. What they should have said is that such a work is <em>still</em> covered by copyright law and you have no right to copy it. </p>

copyright