may I make the following suggestions.
Assuming your mac is not on 24x7 - the mac has maintance scripts which are technically called daily, weekly and monthly and can be run through a termnal command.....i use this occassionally (it helps)
I would also, run the disk utility to check permisions
In addition to MichelPM's questions, here is one more:
What is the size of your hard drive and how much empty space is left?
Note that you need to have an absolute minimum of 10 - 15 GB of hard drive space empty and available at all times for the OS to operate properly - more is better.
If you only have 2 GB RAM, double it if you can - Lion is a memory hog.
The maintenance scripts run in the backgroud when the computer is available in Mac OS X 10.6 and later. It's no longer necessary to manually run the scripts. The article you linked to applies to 10.5 and earlier.
in response to maintanace scripts (i do not debate what you say) however at times when a family member is facebboking viewing youtube and other things along those lines they expeirience a "slow down".... safari does not respond as quickly as it did..... even after clearing history and resestting safari
When the maint scripts are run, every thing is back to normal and the slow down disappears on ML