- White Space Filtering through HTTP Module.
- Merge all inline styles and multiple CSS into one big global css file.
- Try using less images in your web page.
- Optimize your images with image optimizer I use Trout's GIF Optimizer to optimize gif files. PngOptimzer to optimize my PNG files, both the optimizer does not effect the quality of your image.
- If your pagesize is increasing because of ViewState then try to save viewstate on server side. Here is a simpe example to Save ViewState on the File System
10 ASP.NET Performance and Scalability Secrets
Performance Optimization of ASP.NET Applications on Client-side
Also take a look at 15 Tools to Help You Develop Faster Web Pages.