hm. thanks for the answer. i might try out TMP, which i remember you mentioning before, but i don't think i want multiple rows of tabs, since i already have an extra toolbar (developper tools) which already reduces the size of the viewport. this can be a problem because sometimes i like to reduce the window vertically, to compare two pages or to keep an eye on something in the bottom part of my screen while i do something else in the top part (i really needa dual monitor display...). plus, when i said 20 tabs, that's a fairly conservative estimate...
i don't want to end up with so many rows of tabs the viewport is no longer visible at all... (yes i know that slows things down. i just can't help myself).
i have theme windows (one window for mails, with several tabs for different accounts / individual mails, one window for MR, with several tabs for different threads / conversations / messages, one or more windows for whatever else i'm looking at... i rarely have fewer than 5 windows open).
i do like tab scrolling, at least the way ff does it. ie7 is an example of very poor implementation of tabs, if you ask me. i rarely have many tabs open in it since i use it mostly for testing purposes, but it's not at all practical to navigate among tabs. especially since for some idiotic reason they've put a toolbar on the same level as the tabs (and although the toolbars are not locked, i can't seem to drag it anywhere else), so tab space is already limited.
thanks for the explanation about portable ff 1.5, but no worries : i don't actually want to go back that far.
well, if you ever hear of a way to prevent the tab auto-scroll behavior, do let me know, i'd be interested. if you want to test, it always happens on MR with the forum spy, but unless i am mistaken does not *necessarily* occur on other sites... i'll check tomorrow, if i think of it, and confirm. it's getting late here so i'm going to bed now.