Some modern web browsers (as of now - June 2007 - IE 7 and Firefox 2) support OpenSearch plugins. These describe how to submit search query to a web page, so that you don't have to open the page, but enter search text to something else - typically a search box that is displayed as part of browser's toolbar.
This page includes two search plugins, one for Simutrans forum and the other for English wiki.
You can install search plugins either manually by clicking the links below (needs JavaScript) or by the method your browser uses, which may differ. For Firefox, expand the list of search engines and this menu should include items "add xyz".
To install, click install. And that's it!
Same here - click install and you're finished!