How can I read contents from applications' buffer by programming ?

[a qi <free4machine gmail com>]

HI,ALL


for example:

I use firefox to open a webpage,  how can I  read contents of that
page ?  so that I can filter out unwanted information  by programming
.


Do I need gtk  development  tools  since I am using GNOME desktop ?

Any suggestion will be appricated.  Thanks.