Percentage will make your content to be responsive in smaller screens while resizing the window, while for example 500px will always maintain that same value even though you resize the screen, unless you use media queries. Here's a example, Resize the window where the images are on this link to see it work.

&lt;div class="container"&gt;

    &lt;div class="responsiveWidth"&gt;
        ...Responsive Image...
        &lt;img src="https://s-media-cache-ak0.pinimg.com/736x/0d/0b/7d/0d0b7db51cc6665c0943dc0759f88fa6.jpg" width="500"&gt;
    &lt;/div&gt;

    &lt;div class="staticWidth"&gt;
        ...Static Image...
        &lt;img src="https://s-media-cache-ak0.pinimg.com/736x/0d/0b/7d/0d0b7db51cc6665c0943dc0759f88fa6.jpg" width="500"&gt;
    &lt;/div&gt;

&lt;/div&gt;


and your CSS:

.staticWidth {
    width:500px;
    margin:10px;
    border:1px solid #000;
}
.responsiveWidth {
    width:100%;
    margin:10px;
    border:1px solid #000;
}
.responsiveWidth img{
    width:100%;
}


Change Width of Object on Screen Resize
I confess! Being a non-native speaker, I struggle a lot especially when I come across a new word. And I wonder how do native speakers pronounce perfectly even though they read the word for the very first time. There should be some rule/technique? I'm not sure.

Let's take a case. 

If I see a word having 'ch' for the very first time, how do I guess it? Remember, I don't have dictionary. Nor do I have access to this great site when I encounter that word. For example, 

Take the word 'chariot'. Being a non-native with quite limited knowledge of orthography, I know that 'ch' is pronounced as in 'Charles'

But then, imagine, I came across the word 'charade'. Undoubtedly, for me, it is 'ch (as in Charles)-re-d-s'. But then, actually, 'ch' there is 'sh' (as in Shane). 

It's not just 'ch' but it goes for 'g' as well. 'G' as in 'goat' or 'g' as in 'gymnastic'. Is there any source that teaches how to pronounce a letter if it is placed after/before certain letter? Is there any such rule? The one I remember is when a word ends with 'mb', you don't pronounce 'b'. 'Bomb', 'Comb', 'Tomb' and many other words ending with 'b'.  



There are a few more words that add another nail in the coffin of my pronunciation complexity! 


  penis (pee, and not as in 'pen')  asthma (no 'th' pronounced)  Dengue (dengeee)  and many more...

