Currently, search seems to be doing odd things when you search for posts without certain tag(s) using the not operator. For example:
-[css] -[html] should return a list of posts that do not have the CSS or HTML tags, and it correctly looks for that criteria. However, it also seems to change my search query to
"-[css] -[html]" (note the quotation marks) and searches for posts which do not have the CSS and HTML tags, but also contain the words CSS and HTML within them.
The same thing happens whether you search for one or many tags. This doesn't seem to happen if you don't use the not operator on the tags.