Copying an existing HTML page and use it, is that against any copyright law?
<p>I found an online calculator that determines certain parameters I need. However, that calculator can be improved and more information added. I have improved it and now I want to make it public on my new website, however, I don't know anything about online copyright as this is my first attempt to do something similar.
I have copied the HTML page and javascript and customized it to make it better. On the original online calculator and downloaded files, <strong>there isn't any copyright claim.</strong> <em>Does it mean I have the right to use these newly modified files and publish the improved calculator on my website?</em></p>

<p>There doesn't need to be any copyright claim for there to be copyright protection. The protection is given automatically whenever someone authors a work.</p>

<p>If you make money off of your improved version, the owner of the page may sue you for royalties.</p>

<p>The only way to avoid this is to ask him for permission, or to create your page without using any of the source code of the original page.</p>

<p>If you copy and republish the page, it's the same as copying and republishing any copyrighted work. There's no difference for "online copyright".</p>

<p>Automatic copyright isn't a thing everywhere. (although it is in most places.)
If you happen to be in such a place, check your local laws, the page may not have copyright protection. (just where you are)</p>

<p>It's unlikely that the original creator of the calculator will attempt to sue you over it. Though, if you're concerned about that happening you could re-implement most/all of the code and layout.
Without seeing it myself, I don't know how complicated the implementation is.</p>

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