The problem is that when I add a trailing slash at the address bar url localhost/register.php/ the CSS dissapears (is not applied anymore). CSS is in a separate file in a separate dir. Here is the structure:
CSS is invoked in header.html with <link rel="stylesheet" href="css/style.css" type="text/css" media="screen" />
header.html is included in index.php with include 'includes/header.html';
Running apache under Windows 7.
When a trailing slash is added, your browser assumes register.php to be another directory, rather than a file. When relative URLs are specified, the external resource will be sought relative to the subdirectory register.php/ (because of the slash).
Example:
css/style.css > http://localhost/css/style.csscss/style.css > http://localhost/register.php/css/style.css.Fixing
To fix this issue, make use of absolute URLs. Either of the following:
<link href="/css/style.css" ... /><link href="http://localhost/css/style.css" ... /><base href="/register.php" /> (this tag has to be specified within the <head>
<base> suggestion: it has to be specified before any relative URLs. If you specify it after one, such as after the <link> tag, it'll still fail.
<link href="/... is generally called a root relative path.