Why is my queryString preserved?

Hello!

I got a link in a struts 2 app:

<a href="productview.action?productid=<s:property value="id" />" class="a_blue" target="_top" >More info / Order now</a>

the output looks like:

<a href="productview.action?productid=2" class="a_blue" target="_top" >More info / Order now</a>

After entering it the output of all my other links got the param productid as well even dough I did not add it my self like:

<a href="/mysite/welcomeLink.action?productid=2" class="a_white">home/about</a>

The code for the above link is just:

<a href="<s:url action="welcomeLink"/>" class="a_white">home/about</a>

So if any one got the answer why the queryString is preserved just let me know.

Best regards
Fredrik