###!!! ASSERTION: bad width: 'Not Reached', /mozilla-central/layout/generic/nsLineLayout.cpp, line 180 Block(li)(1)@063AD088: Init: bad caller: width WAS 6000000(0x5b8d80) Block(li)(1)@063AD088: UpdateBand: bad caller: width WAS 5994032(0x5b7630) Block(li)(1)@063AD088: UpdateBand: bad caller: width WAS 5988064(0x5b5ee0) Block(li)(1)@063AD088: UpdateBand: bad caller: width WAS 5982096(0x5b4790) Block(li)(1)@063AD088: UpdateBand: bad caller: width WAS 5976128(0x5b3040) nsBlockReflowContext: Block(li)(1)@063AD088 metrics=6000000,0! nsBlockReflowContext: Block(ol)(1)@063ACDF8 metrics=6000000,0! I get this spew on m.www.yahoo.com.

The code that outputs this NOTREACHED is: 167 void 168 nsLineLayout::BeginLineReflow(nscoord aX, nscoord aY, 169 nscoord aWidth, nscoord aHeight, 170 PRBool aImpactedByFloats, 171 PRBool aIsTopOfPage) 172 { [SNIP] 179 if ((aWidth != NS_UNCONSTRAINEDSIZE) && CRAZY_WIDTH(aWidth)) { 180 NS_NOTREACHED("bad width"); So it looks like the page has some line with a gigantic (one might even say "crazy") width. Note that CRAZY_WIDTH() just checks if aWidth is outside the range [-500000, 500000] It's defined here: http://mxr.mozilla.org/mozilla-central/source/layout/generic/nsHTMLContainerFrame.h#57

Yeah, they set the width to 100,000px. They do this in combo_002.css, but I've combined the files for easy test-casing.

I can confirm the bug on Windows 7 x86 with XULRunner compiled from mozilla-1.9.1 sources for firefox, on various links on www.youtube.com browsed with embedded Gecko (with nsIWebBrowser).