hide div tag on mobile view only?

Set the display property to none as the default, then use a media query to apply the desired styles to the div when the browser reaches a certain width. Replace 768px in the media query with whatever the minimum px value is where your div should be visible.

#title_message {
    display: none;
}

@media screen and (min-width: 768px) {
    #title_message {
        clear: both;
        display: block;
        float: left;
        margin: 10px auto 5px 20px;
        width: 28%;
    }
}

@media only screen 
and (min-device-width : 320px) 
and (max-device-width : 480px) { #title_message { display: none; }}

This would be for a responsive design with a single page for an iphone screen specifically. Are you actually routing to a different mobile page?

The solution given didn't work for me on the desktop, it just showed both divs, although the mobile only showed the mobile div. So I did a little search and found the min-width option. I updated my code to the following and it works fine now :)

CSS:

    @media all and (min-width: 480px) {
    .deskContent {display:block;}
    .phoneContent {display:none;}
}

@media all and (max-width: 479px) {
    .deskContent {display:none;}
    .phoneContent {display:block;}
}

HTML:

<div class="deskContent">Content for desktop</div>
<div class="phoneContent">Content for mobile</div>

You will need two things. The first is @media screen to activate the specific code at a certain screen size, used for responsive design. The second is the use of the visibility: hidden attribute. Once the browser/screen reaches 600pixels then #title_message will become hidden.

@media screen and (max-width: 600px) {
  #title_message {
    visibility: hidden;
    clear: both;
    float: left;
    margin: 10px auto 5px 20px;
    width: 28%;
    display: none;
  }
}

EDIT: if you are using another CSS for mobile then just add the visibility: hidden; to #title_message. Hope this helps you!