The web site in question is www.eventid.net; my web based app will redirect the user to the site and send an event id in the url. The redirect will be: http://www.eventid.net/display.asp?eventid=1003&source=Microsoft-Windows-Security-Licensing-SLC
Do you think I can do this?
I have contacted the site owners with no reply.
It's a public website, of course you can.
It'd be a different matter if you were screen-scraping their results for your own application, but from your description that's not the case.
Read through their Terms of Use carefully. Make sure you avoid violating their trademark. If it's not clear that you are redirecting to an external site, you may want to make it clear so your users aren't confused.
If you were operating a web site in Germany, and your site had a deep link to a Stackoverflow article, and that article contained copyrighted code from a German company (posted by an employee, for instance), that company could easily get you in trouble at any German court.
US courts have been much more lenient, so if you are doing business solely in the US, I would not worry too much, as long as you don't violate the Terms of Use here.
So, I think the answer "Of course, it is a public site" does not do justice to the potentially complicated legal issues that can arise when you take the question into an international context.
Some examples (only the big ones make it into English language news):
http://www.linksandlaw.com/courtdecisions-germany.htm
http://www.theregister.co.uk/2005/04/11/heise_not_allowed_to_mention_slysoft/