1) First download IComplex 2.0 from the following website. This is a freeware.
http://www.omicronlab.com/tools/icomplex-full.html
2) Install as shown in the website.
3) After installing the fonts, now it's time to configure your internet browser,
Internet Explorer:
i) From the tools menu, select 'options internet'
ii) From internet options window, click on 'Fonts' (on General Tab)
iii) Click on the drop down list for Language Script. Select Bengali from this drop down list.
iv) Select "Likhan" or "Siyam Rupali" for web page font (of course, you can choose any other Bangla font). Then click OK
Firefox:
i) From Tools menu, select Options
ii) From this Options window, click on Contents
iii) Click on Advanced button in Fonts & Colors section
iv) Click on the drop down list for option Fonts For. Select Bengali from this list.v) Complete all the option fields as in the following image (you may choose your any favourite Bangla font) and then click on OK.