xsl and microsoft:please help me understand

I am totally new to xsl and not know much about standards and stuff

now it is my understanding that IE was the 1st browser to come out with an
xslt implementation. but now, i have IE 5.0 and my xsl documents are
designed on it.

1. is it benifical to stay with IE 5.0. will upgrading/programming on a new
browser release be harmful

2. how do i program to the new browser, just upgrade to the new browser and
i guess the browser parser will validate my xsl? if i program on ie 5.5 or
6.0, will users with ie 5.0 bowsers be able to see without problems what i
have done. also, i have checked my application and it does not work on
bowsers other than ie, is there a short and sweet way to correct this.

3. i am using xml spy and allaire homesite. these r good tools but not
impressive, are there other tools out there.

answers will be appreciated. Thanks in advance.

TP.

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