Why use grid or flow layout?

I have an extensive VB6 background but I'm relatively new to web development and ASP.NET. I see that some people prefer flow layout but to me (because of my background) it doesn't seem as intuitive as grid layout.

What are the pros and cons of each? I don't want to get a month down the road in my development process and realize I should have used the other one.

Thanks!Well, flowlayout is better to me, since it would be nice when you resize the window for the page's contents to get resized too. while gridLayout, things will be static in their place. Usually, its better to use % instead of pixels, so that your webpage will be fit in any screen resolution. But after all its a design matter, it goes back to you.
I personally prefer the flow layout so I dont have to worry about client browser settings.
http://msdn.microsoft.com/library/en-us/vsintro7/html/csconPositioningElementsInWebPages.asp?frame=true
I think you have to consider your clients. If there are going to be a variety of browsers viewing your site(i.e. public site), i think flow layout is safer. By safer, I mean a more predictable appearance. Some of the cross-browser testing I have done has resulted in some unpredictable behavior in mozilla. This fact could be argued, i'm sure, but legacy browsers don't support DHTML so the absolute locations are a problem.
Our site will be an internet site (not intranet) but only the home page will be available to all users. The rest of the site will be for our paying clients only and I expect we can ask them to install the latest IE or whatever is necessary.

So, considering that, what do you think?
Even if they're paying you still don't want to FORCE them to use a particular type of browser or a particular screen resolution or whatnot. Not all web surfers even know how to upgrade I.E. or change their screen resolution to 1024 x 768.

Why make your site user-unfriendly?