Kompx.com or Compmiscellanea.com

CSS. Target Opera only

Windows : Opera 9.5+ [ 1 ] [ 2 ].

Linux : Opera 9.5+ [ 3 ].

CSS targeting Opera web browser only:

This text is red in Opera

HTML / XHTML. Code:

<p>This text is red in Opera</p>

CSS. Code:

doesnotexist:-o-prefocus, p {color: #f00;}

The -o-prefocus pseudo-class allows styling elements for Opera browser only. The code is placed in the common CSS file, not in a separate one as it is in case of Internet Explorer conditional comments.

Source: http://www.opera.com/docs/specs/presto2.12/css/o-vendor/


[ 1 ]

Opera 3.5 - 5.0 ignores "doesnotexist:-o-prefocus" and reads code as p {color: #f00;}. Opera 6.0 - 9.4 ignores the whole code starting "doesnotexist".

[ 2 ]

Internet Explorer 5.5+, Firefox 1.0+, Google Chrome, Safari 3.1+, SeaMonkey 1.0+, Netscape 7.2+, Mozilla 1.5+ ignore the whole code starting "doesnotexist".

Older browsers like Internet Explorer before 5.5 or Netscape before 7.2 or Mozilla before 1.5 seem to ignore the uncommon, Opera 9.5+ specific code ("doesnotexist:-o-prefocus") and apply styles to what they understand - here it is the p tag; making the text in it red.

[ 3 ]

The text is red in Dillo 3.0.1 as well.


Aliosque subditos et thema

 

JavaScript form submit

 

Submitting a form using JavaScript. A dropdown list (form + select + multiple options) is processed without any submit button. Example: --- Select a page --- Linux Windows DOS HTML / XHTML. Code: <form action="action.php" method="post"> <select name="page" required="required" onchange="this.form.submit()"> <option value="" selected="selected" disabled="disabled"> --- Select a page --- </option> <option value="http://www.kompx.com/en/os/linux-1.htm">Linux</option> <option value="http://www.kompx.com/en/os/windows-1.htm">Windows</option> <option value="http://www.kompx.com/en/os/dos-1.htm">DOS</option> </select> <noscript><input type="submit" value="Submit" /></noscript> </form> When an option has been chosen from the dropdown list, the form's state is changed. So the onchange event occurs and JavaScript code in onchange is executed: the process of the form submission in started by the script, not by clicking submit button which is absent. Some server-side script [ 3 ] is meant then to handle the form action. The script is supposed to get what the form sends and have it processed. A PHP script in action.php is used in the example: <?php if (isset($_POST["page"])) {     header("Location: $_POST[page]");     exit; } else {     echo "No options selected"; } $_POST is an array of variables passed to the current script via the HTTP POST method. So $_POST[page] contains the content of the value attribute in a select option. That is, a URL. It is passed from form to PHP script and the script redirects browser to the URL / page selected. HTML code of <noscript><input type="submit" value="Submit" /></noscript> is present in the form as a fallback in case JavaScript happens to be turned off. Then there is a submit button to appear and the form is usable anyway. [ 1 ] As well as Netscape 3.04+, Mozilla 0.6+. [ 2 ] As well as Netscape 3.04+, Mozilla 0.6+. [ 3 ] If a CMS is used, form action may be handled by some of its inbuilt means.

Extract tar.gz

 

Extracting tar.gz files in Linux, command line: tar zxvf file.tar.gz - z : filter the archive through gzip [ 1 ] - x : extract files from an archive - v : list the files processed - f : use archive file The command extracts the contents of a compressed archive to the current directory. Tar creates an archive of one or several files. Then gzip is used to compress it. Or both processes are made at once by tar only, with corresponding options employed. The duality of nature - archived and compressed after - is reflected in the extension of the file ("tar.gz") and requires two procedures to be performed while extracting: decompressing and unpacking. Hence both z (decompress it) and x (unpack it) in the command. [ 1 ] Sources for the option letters description: tar(1) - Linux man page and LinuxCommand.org