Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <head> <script> function ChangeOpacity(x) { // Return the text of the selected option var opacity=x.options[x.selectedIndex].text; var el=document.getElementById("p1"); if (el.style.opacity!==undefined) {el.style.opacity=opacity;} else {alert("Your browser doesn't support this example!");} } </script> </head> <body> <p id="p1">Select a value from the list below, to change this element's opacity!</p> <select onchange="ChangeOpacity(this);" size="5"> <option />0 <option />0.2 <option />0.5 <option />0.8 <option selected="selected" />1 </select> </body> </html>
Result:
W3Schools.com - Try it yourself