Wordpress blocking javascript?
No this is not default behaviour in wordpress. I have added <script> tags to the html view of a page or post no problem.
Did you switch the view after you add the code ? If so, don't. Wordpress will delete all tags if you switch to view back from HTML.
Like Tim said, you probably posted the code into the Visual Editor (doesn't accept any HTML tags, like scripts). You should to the HTML editor to implement your code, but if you want to have it on more than one page, you should open up the Appearance Editor and paste it into your theme where you need it (most likely in the header).