how to remove border from iframe in HTML?

You can easily do it using frameborder attribute of iframe, like code below

<iframe src="url" width="200" height="200" frameborder="0">
     <p>Your browser does not support iframes.</p>
</iframe>

to make it work in all browsers including IE6 you can use frameBorder attribute ('B' is capital)

<iframe src="myURL" width="300" height="300" frameBorder="0" scrolling="no">Browser not compatible. </iframe >

Note: use frameBorder (capital B) for IE, otherwise will not work. But, the iframe frameborder attribute is not supported in HTML5. So, Use CSS instead.

<iframe src="/url" style="width: 100%; height: 400px; border: 0"></iframe>

you can also remove scrolling using scrolling attribute

<iframe src="http://example.org" width="200" height="200" scrolling="no" style="border:0">

Also, you can use seamless attribute which is new in HTML5.

The seamless attribute of the iframe tag is only supported in Opera, Chrome, and Safari.

Remove iFrame border using CSS

If the above solutions doesn't work for you then you can try this CSS

.frameNoBorder {
  padding:0px;
  margin:0px;
  border: 0px
}

This will work, thanks.

For more better output to remove iframe borders use "frameborder="0" hspace="0" vspace="0" marginheight="0" marginwidth="0""

So example

<iframe src="/url" width="100%" marginwidth="0" height="400" marginheight="0" scrolling="No" frameborder="0" hspace="0" vspace="0">Error, iFrame not supported </iframe>

Using Javascript

If you have lots of iFrame in web-page and want to remove borders using Javascript, call this function on page load.

//remove border from all iFrame of page
function removeAllIFrameBorders(){
   if (window.document.getElementsByTagName("iframe"))
   {
      var iFrameElements = window.document.getElementsByTagName("iframe");
      for (var i = 0; i < iFrameElements.length; i++)
         {
            iFrameElements[i].frameBorder="0";   //  For most browsers.
            iFrameElements[i].setAttribute("frameBorder", "0");   //  backup of above.
            iFrameElements[i].contentWindow.document.body.style.border="none";   //  For IE.
         }
   }
}