Q:

Loading images issue - Wordpress and Bootstrap

I don't understand why the loading of my images on http://clinique-esthetique-occitanie.com/
sometimes is really long, and sometimes not.
The website is hosted on a Virtual Private Server (OVH) and I already try to tune Apache (by turning off some modules, turning ExpiresActive On, turning EnableSendfile OFF).
I use Wordpress and I installed W3 Total Cache on it. All the caches are enabled, and I also put in place a CDN with Google App engines in order to lighten my server, but even that doesn't work. As you may see the images are loaded on Google Servers: (host of my application : clinique-esthetique.appspot.com )
For example : http://clinique-esthetique.appspot.com/wp-content/uploads/2013/09/CHIRURGIE-OREILLES-DECOLLEES.jpg
So maybe I was thinking it could come from Twitter Bootstrap, which resize all the images to take the half of the content part (by the css class="col-md-6"). But I don't know what I can do to improve the loading time of my images, which remains (sometimes) really long, and sometimes image doesn't even appear at all.
Thank you very much.
Regards.
Loïc.

A:

Image Resizing does not affect image load time.  A css resize simply forces the image to fit the css requirements.  The image is the same size. 
There are certain plugins you can add to various CMS's that will thumbnail images using a php function.  
Hence image loading is affected by a number of issues.

The size of the Image.  So many times I see people loading large images and then using css to reduce them by 50% or more.  If you never actually use the full size image...compress it in an image editor - you can in some cases reduce its total size in kb by more than 1/2.  This is the process known as image optimization.  This offering from the google development centre might help you.

http://developers.google.com/speed/pagespeed/insights/?url=http%3A%2F%2Fclinique-esthetique-occitanie.com%2F

Congestion between the client and the server.  (Varies)  You can speed up things at this point by using a CDN - there are many commerical CDN'S available - they effectively cache your website and when someone requests the site - the CDN serves the site from the closest available cache server.  This can speed up page load times considerably.  That being said.  CDN's also suffer from location and load. I can show you a number of complaints from people that have moved to CDN's only to have content served up slower.  Also CDN's vary in how they serve a page. Some will server text elements immediately but delay image sending to speed up the content getting to the client's browser first. I would also note that not all images are being served from you CDN.  Some are still coming direct from the server.

Finally I loaded your page from a number of page viewing sites and in all cases the load times were fast. Interestingly browser load times are quite good, but you need to improve your page serve times to mobile devices.  Basically all the optimization you have done only applies to the desktop version of your site.  
Let me know I can assist further.

