News:

Choose a design and let our professionals help you build a successful website   - ITAcumens

Main Menu

HTML Important Questions and Answers - II

Started by Kalyan, Nov 28, 2008, 11:22 PM

Previous topic - Next topic
Go Down Pages1

Kalyan

Nov 28, 2008, 11:22 PM
HTML Important Questions and Answers - II

How can I specify colors?

If you want others to view your web page with specific colors, the most appropriate way is to suggest the colors with a style sheet. Cascading Style Sheets use the color and background-color properties to specify text and background colors. To avoid conflicts between the reader's default colors and those suggested by the author, these two properties should always be used together.

With HTML, you can suggest colors with the TEXT, LINK, VLINK (visited link), ALINK (active link), and BGCOLOR (background color) attributes of the BODY element.

Note that these attributes are deprecated by HTML 4. Also, if one of these attributes is used, then all of them should be used to ensure that the reader's default colors do not interfere with those suggested by the author.

Here is an example:

<body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080" alink="#000080">
Authors should not rely on the specified colors since browsers allow their users to override document-specified colors.


How do I get form data emailed to me?

The only reliable mechanism for processing form submissions is with a server-side (e.g., CGI) program. To send form data to yourself via email, you should use a server-side program that processes the form submission and sends the data to your email address.

Some web service providers make standard form-to-email programs available to their customers. Check with your service provider for details.

If you can install CGI programs on your own server, see the answer to the previous question for a list of useful resources.

If you can't run CGI programs on your own server, you can use a remotely hosted form-to-email services. Note that the provider of a remotely hosted service will have access to any data submitted via the service.

Forms that use action="mailto:..." are unreliable. According to the HTML specifications, form behavior is explicitly undefined for mailto URIs (or anything else other than HTTP URIs). They may work one way with one software configuration, may work other ways in other software configurations, and may fail completely in other software configurations.


Can I prevent a form from being submitted again?

No. The server-side (e.g., CGI) program that processes the form submission must handle duplicate submissions gracefully.

You could generate the form with a server-side (e.g., CGI) program that adds a hidden field with a unique session ID. Then the server-side program that processes the form submission can check the session ID against a list of previously used session IDs. If the session ID has already been used, then an appropriate action can be taken (e.g., reject the submission, or update the previously submitted data).

Ultimately, your server-side program must be smart enough to handle resubmitted data. But you can avoid getting resubmitted data by not expiring the confirmation page from form submissions. Since you want to expire pages quickly when they have transient data, you might want to avoid putting transient data on the confirmation page. You could provide a link to a database query that returns transient data though.


How can I allow file uploads to my web site?

These things are necessary for Web-based uploads:

* An HTTP server that accepts uploads.
* Access to the /cgi-bin/ to put the receiving script. Prewritten CGI file-upload scripts are available.
* A form implemented something like this:

<form method="post" enctype="multipart/form-data" action="fup.cgi">
File to upload: <input type=file name=upfile>

Notes about the file: <input type=text name=note>

<input type=submit value=Press> to upload the file!
</form>

Not all browsers support form-based file upload, so try to give alternatives where possible.

The Perl CGI.pm module supports file upload. The most recent versions of the cgi-lib.pl library also support file upload. Also, if you need to do file upload in conjunction with form-to-email, the Perl package MIME::Lite handles email attachments.


How can I require that fields be filled in, or filled in correctly?

Have the server-side (e.g., CGI) program that processes the form submission send an error message if the field is not filled in properly. Ideally, this error message should include a copy of the original form with the original (incomplete or incorrect) data filled in as the default values for the form fields. The Perl CGI.pm module provides helpful mechanisms for returning partially completed forms to the user.

In addition, you could use JavaScript in the form's ONSUBMIT attribute to check the form data. If JavaScript support is enabled, then the ONSUBMIT event handler can inform the user of the problem and return false to prevent the form from being submitted.
Note that the server-side program should not rely upon the checking done by the client-side script.

source : interviewghost
Go Up Pages1