Javascript variables in HTML attributes
You can add the style using javascript to particular element like this.
script
document.getElementById('myImg').style.width = screen.width + "px";
Html
<img id="myImg" src="images/title.png" style="margin-top: 3%">
Here is a demo
You can't simply call a JavaScript variable inside your HTML. You'll need to have it written by JavaScript or JQuery. You can do it this way :-
<input id="myInput" .../>
<script>
var myVar = "value";
$("#myInput").attr("name", myVar);
</script>
Give the tag an id.
i.e. <img id="xxxx" ...>
Then use
document.getElementById('xxx').setAttribute('width', 'somevalue')
See setAttribute
Or use JQuery as the other poster noted
This should work:
<script>var screenWidth = screen.width;</script>
...
<img src="images/title.png" onload="this.width=screenWidth;" style="margin-top: 3%">