```
<style type="text/css">
<!--
.style1 {
    color: #666666;
    font-weight: bold;
}
.style8 {font-size: 12px; color: #333333; }
.style9 {
    font-size: 12px;
    font-weight: bold;
    color: #FFFFFF;
}
.style12 {font-size: 12px; font-weight: bold; color: #666666; }
.style13 {font-size: 12px; font-weight: bold; color: #0066FF; }
.style14 {
    color: #0043A8;
    font-size: 16px;
}
.style15 {color: #FFFFFF}
.style16 {color: #990000}
.style18 {color: #990000; font-size: 12px; }
.style20 {font-size: 12px; font-weight: bold; color: #575757; }
-->
</style>

```

above stylesheet is enclosed in `<!-- -->` html comments tag. why? I can't get valid explanation for this; some tutorials do this while some doesn't (like <http://www.w3schools.com/css/css_howto.asp> which I think is very valid reference)
['https://Stackoverflow.com/questions/14749629', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1684670/']
It is an antiquated method of hiding content from browsers who are older than the standard that introduced `<style>` or `<script>` tags.

There is no valid use for such a habit anymore and in fact will cause more problems than it fixes.

Unless you are developing a website for peolpe living in the 1990's (like the editors at w3schools)... don't do it!
This is done to avoid displaying the script content in some (old) browsers which don't know about `<style>` markup. See [this](http://lachy.id.au/log/2005/05/script-comments).