Please update to Firefox 19.0.2 Update Firefox to the latest release

Are you trying to install Wordpress on a server? Please contact Wordpress tech support.

You need to run server software if you want to process PHP code.

Firefox can only render HTML code, so if PHP is present then it needs to be processed by the server before sending the resulting HTML code to the browser.

Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (MAC)

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"