Robots.txt disallow help

[virtualreality]

How do I disallow dynamic URLs such as:

myforum-topic1?datecut=0&sortby=subject&order=asc
myforum-topic2?datecut=0&sortby=subject&order=asc
myforum-topic3?pid=10&mode=threaded

I want to disallow only the part after "?", therefore I would like to index myforum-topic1.

I cant Disallow: /myforum-topic1?* because I have hundreds of topics, and that would mean to do it manually for all.

I tried:

disallow /?* and disallow /*?* but when I run my site map generators all URLS with "?" get indexed again.

[dstiles]

Canonical tags in the web page header? Built dynamically you can remove any or all of the querystring fields.

[virtualreality]

and how to do that?

[tangor]

You'll need to review the robots exclusion rules. Can't help much with dynamic since I run none myself, but I do know that wildcards are few to non-existent in robots.txt.

[tangor]

You'll need to review the robots exclusion rules. Can't help much with dynamic since I run none myself, but I do know that wildcards are few to non-existent in robots.txt.

[dstiles]

There's quite a lot of info on canonical tags in the google section of this site.

Basically:
<link rel="canonical" href="http://www.example.com/page.ext" />

where page.ext is something like index.htm or aboutus.php (obviously the basic name of the page in which the canonical tag is inserted). Querystring portions can be added if relevant.

[marketingguru]

RObots.txt is very helpful to give allow and disallow.
rel=canonical is helpful.

[edited by: bill at 10:23 am (utc) on Nov. 28, 2009]
[edit reason] No URL signatures [/edit]