1.CSS-3

<h2 id="css3"></h2>
<style>#css3::before{content:"1.CSS-3";}</style>

2.ATTR-3

<h2 data-title="2.ATTR-3" id="attr3"></h2>
<style>#attr3::before{content:attr(data-title);}</style>

3.IMG-3

<h2><img src="path/to/title3.png" alt=""></h2>

4.B64-3

// PHP GD ⇒ base64 image (see code sample)

5.SVGEM-3

<object data="title3.svg" type="image/svg+xml"></object>

6.CAN-3

<canvas id="can3" width="400" height="60"></canvas>
<script>
 const c=document.getElementById('can3').getContext('2d');
 c.font='32px Arial';c.fillText('6.CAN-3',10,40);
</script>

7.WEBGL-3

// WebGL canvas – omitted for brevity

8.JS-3

<h2 id="js3"></h2>
<script>document.getElementById('js3').innerText='8.JS-3';</script>

9.EVT-3

<h2 id="evt3">(click)</h2>
<script>document.getElementById('evt3').onclick=()=>{event.target.innerText='9.EVT-3'};</script>

10.COM-3

<h2><!--10.COM-3--></h2>
<script>...extract comment...</script>

11.ENC-3

// atob(<base64>) then inject

12.IFR-3

<iframe src="title3.html"></iframe>

13.PDF-3

<embed src="title3.pdf" type="application/pdf">

14.FNT-3

// custom icon font glyphs

15.FRM-3

<input value="15.FRM-3" disabled>

16.OBJ-3

<object data="title3-content.html"></object>

17.EMB-3

<embed src="title3-content.html">

18.SHD-3

<h2 is="shadow-title-3"></h2>
<script>
 class ShadowTitle3 extends HTMLHeadingElement{
   constructor(){super();const s=this.attachShadow({mode:'closed'});
   const span=document.createElement('span');span.textContent='18.SHD-3';s.appendChild(span);}
 }
 customElements.define('shadow-title-3',ShadowTitle3,{extends:'h2'});
</script>

19.B64SVG-3

// <img src="data:image/svg+xml;base64,...">

20.XHR-3

<h2 id="xhr3"></h2>
<script>fetch('title3.txt').then(r=>r.text()).then(t=>xhr3.innerText=t);</script>