I recently installed phpbb and a theme for it, but, the theme is based on fluid width. So everytime the resolution changes, the width of the forum changes too. I was wanting to add a logo and a gallery on the home page, but this fluid width thing is irritating. I'd like to fix the width at about 70%.

I'm a noob to CSS, so I'd be glad if someone could help

www.indiaos.com is the URL

70% of what? A percentage-based width is a fluid width.

If you want your width fixed, specify it in pixels.

well, I don't know !!
I want the forum's width to remain as it is now, without it changing its width during resolution change or when some sidebar is opened in FF/IE which again reduces its width.
Hope you understand .

hellmet, I'd recommend leaving it fluid. It creates a better user experience.

What I have done in the past though is define min and max widths. Beware of problems with IE though:
http://www.svendtofte.com/code/max_width_in_ie/
http://www.cssplay.co.uk/boxes/minwidth.html
Or single items inside of the document I defined as having a set width, just that part though, like a video player column, or image slide show or similar