Why I am sent back to Step 1 from Step3 in install.php?

Please make sure that the PHP setting "file_uploads" is set to "On". In some versions of PHP the POST variables would get lost on multipart forms when this option has a blank or Off value.
The easiest way to check all criteria at once is to download Check Requirements script and place it to your website.

Technical FAQ

Why isn't there any buttons in the editor section? / The editor buttons do not work with Firefox 3 / Sending e-mails using feedback forms or mailinglists fails / Why do I see strange symbols when I open install.php? / Why do I see a blank page when I open install.php? / Why do I see a blank page after a successful installation? / Why I am sent back to Step 1 from Step3 in install.php? / Why install.php hangs during Step4? / How can I change the database connection data? / Setting the database port to anything else than 3306 doesn't work / Why do I get an error if I try to add pictures or files into article? / Why I can't upload big files in File Manager? / Why I can't download big files in File Manager? / Why I see the word "undefined" instead of the real contents of article? / When I open an article in the editor-window, Window Installer popup appears / I get "500 Internal Server Error" when opening install.php / I get error "Unable to connect Saurus License Server!" / I get "ERROR! This license key is already used by another website!" / I get "Error! Receiver e-mail in mail form has been changed by unauthorized persons." / I have defined the right character set, but still wrong symbols are displayed. / Why doesn't my alias work? / How to make a private key to use for the E-commerce module? / I get error "Page not found" after logging into the admin area. / Backslashes "\" appear in articles after saving / The download dialog opens several times after one another / I get message "Due to technical difficulties this site can not be displayed. Check back soon!" / What does "open_basedir restriction in effect" error in Error Log mean?