I made some custom links on a page to go to a predefined search by:

function submitform(){ document.predefinedsearch.submit();}

mixed

so now this links shows all instances which have "mixed" as value

I was wondering if this can be done in a way like:

http://www.thegreenskirt.nl/site/index.php?p=search&value=mixed
or
http://www.thegreenskirt.nl/site/index.php?p=search&tag=mixed

You can use
http://www.thegreenskirt.nl/site/index.php?p=search&words=mixed

hmm I was close...thanks!!