I see questions asked frequently about FireFox rendering problems in Asp.Net forums.
What is "rendering engine"?
A rendering engine, also known as a layout engine, is the code that tells the browser how to display web content and available style information in the browser window
Here are some options to solve those:
Always check rendered web pages for XHTML compatibility using the W3C tests at http://validator.w3.org
. Most issues will fixed by fixing all non standards compliant HTML.
Set clientTarget="UpLevel" in Page Directive. This will override automatic detection of browser capabilities and specifies how a page renders for particular browser clients.