how to get my website running on old computers

I'm currently working as a web developer and yesterday I finished some javascript stuff (filtering). The web it's about the typical case about showing a list of items to the customer.

I made my tests and all seemed go run smooth and well so I told my boss and applied the changes on the production site.. some minutes later and I was phoned by him telling me that he had performance problems running the site in some specific conditions (where the items list was bigger).

Despite in my PC all was still running flawless I understand that there are many differences between our computers to take care of:

• He was using Windows (I use Linux).


• Different hardware specifications: for instance, I have 4 gb of ram (He likely doesn't).


• He uses I.E while I'm using Firefox.

Despite of this, I still can't believe the difference can be so big.. but I realize the site must be able to run even in old PCs, as far as a good amount of users will have a low PC spec.

So I was wondering if you use any kind of patterns, tools or whatever in order to develop websites which are able to run on the maximum range of machines.

For instance, I was thinking in adding some kind of pagination for those cases where the number of items exceeds some value.