Duplicate: http://stackoverflow.com/questions/30251/tables-instead-of-divs#30271 and http://stackoverflow.com/questions/83073/div-vs-table#83121
I am working on building a web app using ASP .NET MVC (needs to run on IE 7, FF 3.0), does it matter if i were to use tables rather than css for positioning and design?
As a developer I haven't had a chance to work with css.
Use tables when you really do want to show tabular data.
Otherwise you really ought to be using CSS for your layout.
The main reason is that CSS works better for "unusual" browsers like the following:
If you work for the US Government that last one is a legal requirement.
Also see these questions:
http://stackoverflow.com/questions/30251/tables-instead-of-divs
http://stackoverflow.com/questions/83073/div-vs-table
Apart from all the "tables are evil" school of thought, you'll find it much easier to change the design in the future if you use pure css layout.
In addition, your mark up will a whole lot simpler and easier to "read".
Take a look at css. It shouldn't take more than a day to get up to speed.
Yes, it matters. The most convincing argument that I've used in favor of CSS over tables is that screen readers (for the visually impaired) trip over tabular layout. That's a good argument by itself, but it gets a whole lot better when you take into account the fact that Google reads your web site just like a screen reader would. If you want Google to have an easier time indexing your site, use CSS for layout. Tables are for tabular data.
Yes if your application UI needs to be of high standards. No, if you are just learning to master some adhoc concept or coming up with a quick prototype. Benefits of CSS vs. Tables are well discussed. With CSS, a web site become more agile and accessible, have a look at CSSZen garden.
On a side note, HTML DOCTYPE declaration and validation are equally important. Lest you would spend time fixing styles for every browser