backlinks hidden in the html and counted by google but not showed on the page?

i was checking my competition today and i have found one website that has a lot of backlinks from homepages of other websites.
anyway if i check the pages i do not find the link.
i only can see it in the html.

and it is something like that

<div id='bbbc3a16db409fa9eda6fce3d02292eb1'> <a href="hxxp://nameofthesite.com" target="_blank">toys</a>
<script>security_modules('bbbc3a16db409fa9eda6fce3d02292eb1');</script>
<!-- 802a2cbaf5ba46d31cdee3fb09098df0 --></body>
</html>

can anybody explain to me how they do this?
are they the owner of those other websites?
why is the link hidden and not visible on the page?

its prob hidden with css, check the page with no page styles and see if you can find it.

For firefox go to View pulldown -> Page Style -> No Style

whats the website so we could look at the code
of either the css or the javascript because he is calling a function named "security_modules"

syns0r said:

its prob hidden with css, check the page with no page styles and see if you can find it.

For firefox go to View pulldown -> Page Style -> No Style

Click to expand...

yes...found it.
it is hidden in with the css.

anyway...the next question is: why are they doing this?

you can also write like this

<noscript><a href="http://blablabla">keyword</a></noscript>

hidden links, counted as backlink