Setting width for the Tab key can change the look for textboxes and <pre> element. With the tab-size CSS property you can set the length of spaces rendered for the tab character.
#element {
/* set size of tab key to 4 white spaces */
-moz-tab-size: 4;
tab-size: 4;
}
By default, the tab character is set to 8 spaces.
The prefix -moz is required for Firefox, even for its latest version.
Tab Character Code for HTML Pages
The code 	 renders a tab character in web pages.
Only the <pre> tag or elements having CSS white-space: pre will display the tab character.
Demo
for($i=0; $i<10; $i++) { if($j > 10) { echo 'Hello'; } }
HTML & CSS
<pre id="demo">
for($i=0; $i<10; $i++) {
	if($j > 10) {
		echo 'Hello';
	}
}
</pre>
#demo {
-moz-tab-size: 8;
tab-size: 8;
}