Do you guys have some best practise advise on the output size of web pages. The smaller the better ofcourse. Im talking about non cached output. Id rather not return 1 MB pages.
If your users are on slower connections, then work out the slowest connection speed you need to support and the maximum acceptable page load time, and size your pages accordingly. But do measure and monitor your page rendering times (I suggest looking at the mean, the median and the 90th percentile).
A good total page size will vary depending on the type of site you have and the content you're delivering. For me a 200kb page is large but for some this is huge and others this might be small. It is always a good idea to test/benchmark your site loading times. The FireBug extension for FireFox is handy for this.
Another option for some types of content is to use AJAX calls to load data bit by bit as needed after the initial page load.
Are you talking ASP, or ASP.NET? If it's ASP.NET, be mindful of the size of the Viewstate variable/field that gets embedded in the page. Any form post-backs from the browser have to send this hidden field with the request, and if you're not careful about how you're storing state in the page, it can get very large very quickly. You don't want to have your users uploading upwards of 256 KB every time they click a button or control on a page.
There's a nice little Firefox extension called Viewstate Size that will place this information in the status bar.