Get the bookmarklets from http://geocities.com/urdutext/
The FireFox Urdu keyboard, for example, works on the following sites:
GOOGLE
GOOGLE-GROUPS
JANG
GMAIL (BASIC HTML MODE)
On GOOGLE's search box, for example, type:
aslam elikm
Now click on the URDU button (the bookmarklet) on the FireFox bookmarks
toolbar. The text will convert to Urdu:
اسلام علیکم
When writing assume the CRULP's phonetic keyboard layout.
For sites, where the bookmarklet won't work, there is a second PAD
bookmarklet, which opens a TEXTPAD window, in which you can write, and
then convert to Urdu with the first bookmarklet. The Urdu text can then
be CUT-n-PASTE anywhere.
The bookmarklets are written in javascript, so the script can be
inspected (and modified). By changing the ASCII mapping table, it can
support Arabic and Farsi too.