Let's assume this was a one-time mistake by the website, and is enshrined in a cookie from the site, or a file being used by Firefox from its cache.

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

"3-bar" menu button (or Tools menu) > Options > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"

In the dialog that opens, you can remove the site's cookies individually.

Then try reloading the page. Does that get the desktop site?

If that doesn't help, it's possible that the site is not able to accurately read the Firefox "user agent" string, the identifier sent by Firefox to websites. If you use my test page, what do you see in red?

https://jeffersonscher.com/res/jstest.php

Thanks for the help. Here is what is in red: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:37.0) Gecko/20100101 Firefox/37.0

Hi fbcjoe, the user agent string looks fine. Hopefully clearing the cookies will fix it. If not, hmm, can you try accessing the sites a different way, for example, through search results?

What are the dimensions of the browsing window? Some website change automatically to mobile view if you make the window too small.

Can you attach a screenshot and possibly post some links?

• http://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

• Use a compressed image type like PNG or JPG to save the screenshot
• Make sure that you do not exceed the maximum size of 1 MB

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I also needed to update flash. Thanks