How can I stop displaying webpage?

Question

For example: suppose I designed a website only for mobile version and if I try to switch in desktop. how can I give a kind of alert saying that- "To be viewed only in mobile" or something????

Answer 1

You can use CSS media queries for that:

@media only screen and (max-width: 768px) {
    /*something*/
}

Every device with a width of 0px to 768px will will get the styles in that rule set.

Alternatively, you can use JS if you want to show a JS alert. (alert('hey'))

Here is and MDN doc of the topic: https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Using_media_queries

Answer 2

You can do something like this:

<div class="content">
<!-- your content -->
</div>

<div class="fallback-content">
<!-- your fallback content -->
</div>

<style>
.content{
  //your style
}
.fallback-content{
   display: none;
}

@media(min-width:600px){
 .content{
   display: none;
 }
 .fallback-content{
   display: block;
 }
}
</style>