Internet Explorer 7 and 8

Open the "Tools" menu and click the "Security" tab then the "Internet" symbol. Click the Custom Level button, to open the Security Settings dialog box. In the Settings list, scroll down to "Scripting". Under Active Scripting, click the radio button to the left of "Enable", so that a coloured dot appears in it. (Click "Disable" if you want to disable JavaScript.)

Firefox

Open the "Tools" menu (Windows) or the Firefox menu (OS X). Select "Options" (Windows) or "Preferences" (OS X), to open a dialog box. In the row of coloured icons at the top, click "Content". Click the check box to the left of "Enable JavaScript" so that a tick appears. (Click again to remove the tick if you want to disable JavaScript.) Click "OK" to close the dialog box.

Chrome

Click the spanner icon near the top right to open the menu. Select "Options", to open the Google Chrome Options dialog box. In the Google Chrome Options dialog box, click the "Under the Bonnet" tab. In the Privacy section, click the "Content settings" button. In the Content Settings dialog box, click "JavaScript" in the list of Features. (Click the "Do not allow any site to run JavaScript" radio button if you want to disable JavaScript.) Click "Close" to close the Content Settings dialog box. Click "Close" to close the Google Chrome Options dialog box.

Opera

Open the "File" menu (version 6) or the "Tools" menu (versions 7, 8 and 9). Point to "Quick preferences". In the submenu that appears, click "Enable JavaScript" to add or remove the tick. If you are using Mac OS X, then you need to select "Quick preferences" on the Opera menu, instead of the Tools menu. Click the "Allow all sites to run JavaScript (recommended)" radio button.